* Re: [Lse-tech] Re: Patch and Performance of larger pipes [not found] <OF2428DABF.B9AD95A4-ON86256AEA.005A4949@raleigh.ibm.com> @ 2001-10-24 19:39 ` Hubertus Franke 2001-10-30 18:31 ` Hubertus Franke 0 siblings, 1 reply; 5+ messages in thread From: Hubertus Franke @ 2001-10-24 19:39 UTC (permalink / raw) To: Kenneth Rozendal; +Cc: lse-tech, linux-kernel * Kenneth Rozendal <kenroz@us.ibm.com> [20011019 12;28]:" > Hubertus, > > Since the vast majority of all use of pipes involve very small writes > (commonly one line at a time), it would be useful to see the impact on this > case. Any solution probably needs to show insignificant degredation in > this case. The two interesting endpoints are when the reader is faster > than the writer (pipe mostly empty) and when the writer is faster than the > reader (pipe mostly full). Most use of pipes will stabilize into one of > these two cases. > > Thanks, > Ken > As requested by Ken, we measured pipes bandwidth for small writes and reads (32,128,512 bytes) with different computation time spend either after read/write. In saturated state leads to the pipe typically being full or empty. Here are the results which compares our pipe expansion patch and Manfred's patch over vanilla kernel when run with pipeflex. As can be seen, our patch does not have any significant impact in this situations. Manfred's patch too shows no impact when the pipe is typically empty, i.e. readers are waiting. However, in the other case, when the pipe is typically full, i.e writers are waiting, for small transfer sizes and small delays on the reader, there is substantial benefit, which however fades for larger transfer sizes and/or larger read delays. In the previous messages, we had shown that our patch actually improves significantly over vanilla and larger transfer sizes while Manfred's patch degrades. Again, no clear answer to what is the right approach of doing things. Any thoughts.... -- Hubertus Franke + Rajan Ravindran R/W - Read and Write #Bytes over the pipe. R.Compute - Computation delay between each read W.Compute - Computation delay between each write. 2-way ----- Pipe Size (W.Compute=0) %imp R/W R.Compute 4k 8k 16k 32k Manfred 32 10 -1.88 -1.85 -1.99 -2.02 26.28 32 100 -0.53 -0.37 -0.28 -0.28 4.54 32 1000 -0.02 -0.03 -0.01 -0.02 0.44 128 10 -1.57 -2.17 -2.39 -1.81 15.69 128 100 0.03 0.02 -0.02 -0.2 4.18 128 1000 -0.05 -0.02 -0.07 -0.04 0.61 512 10 -0.19 -1.41 -1.75 -2.6 0.88 512 100 -0.35 -0.16 -0.14 -0.32 4.39 512 1000 -0.05 0.18 0.18 0.37 0.64 Pipe Size (R.Compute=0) %imp R/W W.Compute 4k 8k 16k 32k Manfred 32 10 -1.75 -1.28 -1.16 -0.82 1.84 32 100 0.03 -0.16 -0.04 0.14 -0.02 32 1000 -0.18 0.01 0.21 0.03 0 128 10 -1.09 -1.54 -2.24 -2.39 1.92 128 100 0.52 0.91 1.1 0.98 -0.07 128 1000 0.05 0.07 0.08 -0.12 0 512 10 -4.97 -7.09 -7.34 -6.54 3.31 512 100 2.07 1.98 1.98 2.18 -0.28 512 1000 0.19 0.42 0.23 0.43 -0.02 UP -- Pipe Size (W.Compute=0) %imp R/W R.Compute 4k 8k 16k 32k Manfred 32 10 -1.8 -1.33 -1.57 -2.2 29.59 32 100 -0.15 -0.12 -0.41 -0.43 4.13 32 1000 -0.01 -0.03 -0.04 -0.03 0.44 128 10 0.13 -0.02 -1.83 -2.83 27.76 128 100 -0.07 -0.17 -0.61 -0.74 4.05 128 1000 -0.02 -0.03 -0.07 -0.07 0.38 512 10 -1.14 -2.51 -4.69 -6.93 24.56 512 100 -0.12 -0.45 -1 -1.44 3.6 512 1000 0 -0.04 -0.11 -0.13 0.45 Pipe Size (R.Compute=0) %imp R/W W.Compute 4k 8k 16k 32k Manfred 32 10 -0.69 -0.67 -1.7 -0.55 0.19 32 100 -0.32 -0.25 -0.17 -0.1 0.17 32 1000 -0.1 -2.14 -0.11 -0.05 0.03 128 10 -1.87 -0.71 -0.67 -0.43 -0.67 128 100 -0.14 -0.14 -0.22 -0.11 -0.02 128 1000 -0.02 -0.4 -0.03 -0.03 -0.07 512 10 -0.2 -0.13 -1.45 -0.78 -1.67 512 100 -0.06 -0.21 -0.07 -0.14 -0.11 512 1000 0 -0.11 -0.03 -0.19 -0.01 > > Ken Rozendal > STSM - Linux kernel technology lead > IBM Linux Technology Center > (512)-794-1163, IBM Tie-Line 450-9015 > kenroz@us.ibm.com > > > > > Hubertus Franke <frankeh@watson.ibm.com>@lists.sourceforge.net on > 10/19/2001 08:52:51 AM > > Please respond to frankeh@watson.ibm.com > > Sent by: lse-tech-admin@lists.sourceforge.net > > > To: Manfred Spraul <manfred@colorfullife.com> > cc: linux-kernel@vger.kernel.org, lse-tech@lists.sourceforge.net > Subject: [Lse-tech] Re: Patch and Performance of larger pipes > > > > Well we did for all the 3 benchmarks.... > > * Manfred Spraul <manfred@colorfullife.com> [20011018 14;07]:" > > Could you test the attached singlecopy patches? > > > > with bw_pipe, > > * on UP, up to +100%. > > * on SMP with busy cpus, up to +100% > > * on SMP with idle cpus a performance drop due to increased cache > > trashing. Probably the scheduler should keep both bw_pipe processes on > > the same cpu. > > > > I've sent patch-pgw to Linus for inclusion, since it's needed to fix the > > elf coredump deadlock. > > > > patch-kiopipe must wait until 2.5, because it changes the behaviour of > > pipe_write with partial reads. > > > > -- > > Manfred > > > <<< Manfred's patch cout out >>> > > > > Ok, at the request by Manfred Spraul we also ran his <single-copy> > patch. Manfred patch has applied over 2.4.13-pre13 and the results are > compared > over its base vanilla kernel. Our numbers still are %-improvements numbers > of patched 2.4.9 kernel vs. 2.4.9 vanilla. > Manfred's numbers are added as an additional column. > > << Bottom-line >> > > Our patch does better for <Grep> and <Pipeflex> benchmark and > <LMBench> on low transfer sizes for large Pipe-Buffers. > This is only relevant for SMP systems as we have enabled the patch > only for SMP. > > Manfred's patch does better for <LMBench> and beats our patch across > configurations. But it lacks even vanilla for more realistic apps. > The same observation holds for UP. > > We have not measured CPU utilization etc. > As stated in my earlier message, bw_pipe doesn't have a lot of real > applicability, but I am willing to be re-educated here. > > -- Hubertus > > PIPE: Buffer Expansion > ---------------------- > > In this we will report on some experimentation to improve Linux pipe > performance. There are two basic parameters that govern the Linux pipe > implementation. > (a) PIPE_SIZE is the size of the pipe buffer. > (b) PIPE_BUF is the maximum number of bytes an application > can write atomically to the pipe. > > In the current implementation size of pipe buffer is PAGE_SIZE (most > architectures that is 4kB, and the PIPE_BUF is fixed to 4kB (and for > ARM=PAGE_SIZE). > > We wanted to experiment with larger pipe buffer support and higher > concurrency of read and writes. Therefore we experimented with the > following items: > > (A) expanding the pipe buffer size from 1 page to 2,4,8 pages. > > (B) improving the pipe's concurrency of read and write by introducing > intermittent activation of pending readers/writers rather than at > the end of a pipe transaction (read/write). The PIPE_BUF > atomicity constraint is still observed. We therefore introduce > the term of a PIPE_SEG which is a multiple of the PAGE_SIZE and > determines when to wake up pending readers and writers. > > Consider the pipe buffer size to be 32k. The space available to > write on the pipe is 32k and the data which is coming to be > written onto the pipe is also 32k. By keeping the segment size > as 4k, write the first 4k of the total 32k data instead of > writing the entire 32k data, and inform the reader process that > some data is there to be read, and the writer process proceeds > with the next 4k. By that time reader process starts reading > the available data. Intuitively this should create > more concurrency. > > Throughout this experimentation, we kept the PIPE_BUF (atomicity > guarantee) constant at 4kB. > > Benchmarks > ---------- > > The benchmarks we ran for measuring the performance of pipes are > LMBench, Grep, and Pipeflex. The description of these are below. > While LMBench is a widely used OS-Benchmark, we found that Grep and > Pipeflex model more real applications. All are descripted in more > detail below. All applications use different data transfer sizes > aka chunk sizes shown as TS. We report on the two aspects of our > implementation, i.e. larger pipes and intermittent activations > (PIPE_SEG) which is always 4k. All results are shown as % improvement > over the baseline kernel (2.4.9) and all these benchmarks are run on a > 2-way Pentium II, 333Mhz machine. > > Results Summary: > ================ > > UP + 1-way SMP: > --------------- > Neither (A) nor (A)+(B) showed any improvements. Instead degradations > of up to 30% are observed. Obviously our approach/patch does not > make any sense on the 1-way systems. > > N-way SMP: > ---------- > > 1. Increasing the pipe buffer size (A) increasingly improves the > performance of the Grep benchmark by upto 165% for size 32kB. > However, Grep does not show any added benefit nor > degradation utilizing (A)+(B), i.e, expanding the pipe buffer > size AND introducing the segment size=4kB. > > 2. For LMBench, (A) alone shows some improvements for small transfer > sizes (TS<PIPE_SIZE). For TS>>PIPE_SIZE we observe degradation. > Introducing (A)+(B) shows even better improvements for small TS > with very small degradations for larger TS. > > 3. For pipeflex (A) provides increasing benefits with upto 358% > improvements, without any loss at the low end. When introducing > (A)+(B), the benefits drops but are still substantial. > > Based on the results it is clear that expansion of PIPE_SIZE AND > PIPE_SEG introduction gives better performance for some scenarios. > > > Grep > ---- > > This benchmark measures the time taken to grep for some unexisting > pattern on a 50mb file. ie. cat 50mbfile | grep "$$$$". We assume a > warm file cache. > > LMBench > ------- > > LMBench provides a tool to measure the bandwidth of the pipe > (bw_pipe). bw_pipe creates pipes between two processes and moves 10MB > through the pipe in 64KB chunks. We altered that code by providing the > chunk size as a variable input parameter. ie. bw_pipe [2,4,...,32] > > Pipeflex > -------- > > As LMBench does continuous read and write over the pipe in a > synchronous manner (which is not the case in real life), we studied > some test cases which uses pipes(grep, wc, sort, gunzip, ..), and > based on that we have written this pipeflex benchmark. > > Here a write process writes smaller chunks continuously and the reader > process generates a number between [0.5*r .. 1.5*r] microseconds, and > spends that time for computation after each pipe reads. > > A parent process clones 'c' child processes and 'c/2' pipes such that > 2 processes shares one pipe. > ie. pipeflex -c 2 -t 20 -r 500 -s 4 > > c : number of children/threads to launch (should be EVEN) > t : time for which each run of the test should be performed. > r : microseconds spend in computation after each pipe reads. > s : data to transfer over pipe in Kilo bytes. > > > Dynamically assigning values for PIPE_SIZE and PIPE_SEG > ------------------------------------------------------- > > In our current implementation, the size of PIPE_SIZE and PIPE_SEG can > be changed dynamically by writing the values into the newly created > /proc/sys/fs/pipe-sz file through a string having the following > format: > > Po So > > where Po is the Pipe size order > and So is the Segment size order. > > Pipe size will be calculated as PIPE_SIZE = (1 << Po) * PAGE_SIZE. > Segment size will be calculated as (PIPE_SIZE >> So). > > Similarly 'Po' and 'So' can be read through the same proc file. > > * The notation we use in tables for PIPE_SIZE and PIPE_SEG are PS and > SS respectively and TS is the Transfer Size over pipe. > > 2-way (% improvement) Results > ============================= > > Grep > ---- > > PS (A) (A)+(B) Manfred > -- --- ------- ------- > 4k -0.87 -0.95 39.9 > 8k 50.84 50.12 > 16k 107.97 115.86 > 32k 165.25 164.14 > > > LMBench > ------- > (A) (A)+(B) > > --- ------- > > > PS PS > > TS 4k 8k 16k 32k 4k 8k 16k 32k > Manfred > -- -- -- --- --- -- -- --- --- > ------- > 2k -0.3 3.26 4.25 3.83 -0.3 2.98 4.25 4.04 > 54.1 > 4k -2.18 18.97 18.59 18.59 -2.18 18.59 18.59 18.59 > 21.0 > 6k 0.34 13.08 32.7 49.57 0.3 35.63 39.76 55.94 > 69.2 > 8k 0.14 3.02 0 -0.82 13.87 31.59 50.82 75.27 > 63.2 > 12k 0.34 -24.09 -18.74 -12.57 0.34 4.4 -14.86 8.23 > 38.3 > 16k 1.47 -8.88 -14.16 -16.03 1.4 14.42 9.48 13.86 > 37.5 > 24k 1.17 -13.9 1.65 -23.59 1.17 1.65 -2.72 1.2 > 31.2 > 32k 0.66 -14.77 -19.83 -25.63 0.66 -3.2 -6.59 -2.92 > 27.2 > 64k x x x x x x x x > 22.84 > 128k x x x x x x x x > 29.7 > > > Pipeflex > -------- > > (A) (A)+(B) > --- ------- > > PS PS > TS 4k 8k 16k 32k 4k 8k 16k 32k > Manfred > -- -- -- --- --- -- -- --- --- > 2k 0.00 0.00 -0.27 -0.27 0.00 -0.27 -0.27 -0.27 > -24.1 > 4k 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 > -42.0 > 6k 1.61 -1.82 11.46 10.28 1.61 -9.53 9.53 6.75 > -10.86 > 8k -2.00 46.20 46.31 46.31 -2.00 -11.08 7.17 23.73 > -15.9 > 12k -2.93 54.13 64.58 93.31 -2.93 51.62 46.08 84.22 > -14.9 > 16k -3.34 49.95 163.09 162.67 -3.34 51.82 45.57 85.92 > -14.4 > 24k -3.56 50.37 135.50 183.46 -3.56 49.95 134.97 144.40 > -15.9 > 32k -1.40 54.99 143.29 358.75 -1.40 55.75 142.32 147.37 > -17.7 > 64k x x x x x x x x > -15.01 > 128k x x x x x x x x > -15.14 > > > 1-way (% improvement) Results > ============================= > > Grep > ---- > > PS (A) (A)+(B) Manfred > -- --- ------- ------- > 4k -0.47 -0.47 -49.78 > 8k 1.9 -2.73 > 16k -2.73 -2.73 > 32k 1.9 -2.73 > > > > LMBench > ------- > (A) (A)+(B) > --- ------- > > PS PS > TS 4k 8k 16k 32k 4k 8k 16k 32k > Manfred > -- -- -- --- --- -- -- --- --- > ------- > 2k 0.49 4.42 -3.88 -10.13 0.49 11.02 -7.68 -12.06 > 5.91 > 4k -0.5 -1.08 -22.17 -8.6 -0.5 -0.95 -18.65 -4.86 > 24.28 > 6k 3.73 -19.03 -24.23 -18.56 3.73 -15.85 -24.68 -12.44 > 55.17 > 8k 0.82 -33.43 -31.92 -30.19 0.82 -34.38 -25.41 -12.81 > 35.34 > 12k 1.39 -24.06 -30.67 -27.88 1.39 -24.43 -29.79 -27 > 20.39 > 16k -0.87 -29.16 -31.27 -29.73 -0.87 -28.53 -31.97 -28.97 > 24.8 > 24k 0.16 -28.79 -31.87 -28.37 0.16 -28.16 -31.61 -28.66 > 32.72 > 32k 0.35 -28.91 -30.73 -27.23 0.35 -28.77 -31.6 -28.77 > 34.89 > 64k x x x x x x x x > 38.7 > 128k x x x x x x x x > 41.6 > > Pipeflex > -------- > > (A) (A)+(B) > --- ------- > > PS PS > TS 4k 8k 16k 32k 4k 8k 16k 32k > Manfred > -- -- -- --- --- -- -- --- --- > ------- > 2k 0.00 -0.54 -0.80 -1.07 0.00 -0.54 -0.80 -1.07 > -23.66 > 4k -0.14 -0.69 -1.80 -2.21 -0.14 -1.10 -1.80 -2.49 > -41.97 > 6k -0.19 -0.19 -2.41 -2.02 -0.19 -0.19 -2.12 -1.16 > -22.09 > 8k -0.30 -1.86 -6.41 -6.41 -0.30 -1.19 -3.80 -2.61 > -39.97 > 12k -0.33 -1.43 -4.56 -4.01 -0.33 -1.43 -3.84 -3.51 > -55.71 > 16k -0.18 -1.77 -4.47 -4.56 -0.18 -1.15 -4.78 -3.85 > -64.37 > 24k -0.37 -2.21 -6.94 -5.26 -0.37 -1.51 -6.07 -4.89 > -72.98 > 32k -0.42 -2.98 -7.12 -5.18 -0.42 -1.75 -7.06 -5.77 > -77.19 > 64k x x x x x x x x > -82.57 > 128k x x x x x x x x > -84.91 > > UP (% improvement) Results > ========================== > > Grep > ---- > > PS (A) (A)+(B) Manfred > -- --- ------- ------- > 4k -0.53 1.61 -53.49 > 8k -2.58 -1.56 > 16k -4.55 -4.06 > 32k -3.08 -4.06 > > > LMBench > ------- > (A) (A)+(B) > --- ------- > > PS PS > TS 4k 8k 16k 32k 4k 8k 16k 32k > Manfred > -- -- -- --- --- -- -- --- --- > ------- > 2k 7.38 1.17 -15.28 -18.07 4.18 -0.36 -14.32 -20.55 > 16.35 > 4k -1.73 -0.5 -31.7 -26.94 -1.21 5.61 -21.75 -5.17 > 20.58 > 6k -0.3 -22.33 -26.78 -23.36 -0.9 -17.31 -29.61 -19.5 > 73.06 > 8k 7.8 -35 -33.75 -30.65 1.71 -37.11 -29.45 -18.03 > 30.43 > 12k -1.09 -25.99 -36.7 -35.77 0.13 -27.76 -35.56 -34.21 > 13.78 > 16k 0.08 -31.39 -35.37 -34.28 1.2 -30.93 -36.18 -34.18 > 17.47 > 24k 0.42 -32.06 -36.15 -34.65 0.63 -32.28 -36.82 -34.98 > 22.03 > 32k 0.82 -31.52 -35.71 -33.41 1.8 -32.11 -36.49 -34.52 > 24.87 > 64k x x x x x x x x > 26.66 > 128k x x x x x x x x > 41.27 > > > Pipeflex > -------- > > (A) (A)+(B) > --- ------- > > PS PS > TS 4k 8k 16k 32k 4k 8k 16k 32k > Manfred > -- -- -- --- --- -- -- --- --- > ------- > 2k -0.27 -0.27 -0.80 -1.06 -0.27 -0.27 -0.80 -1.06 > -24.4 > 4k -0.27 -0.68 -1.77 -2.31 -0.14 -0.54 -1.63 -2.18 > -42.3 > 6k -0.66 -0.94 -3.85 -3.94 -0.47 -0.66 -2.63 -1.97 > -22.9 > 8k -0.58 -1.96 -6.88 -6.88 -0.58 -1.30 -4.49 -3.48 > -40.5 > 12k -1.00 -2.16 -5.59 -5.59 -0.84 -1.79 -4.75 -4.54 > -56.7 > 16k -1.22 -2.40 -6.02 -6.18 -1.14 -2.10 -6.06 -5.34 > -65.4 > 24k -1.50 -3.41 -8.68 -7.23 -1.72 -2.76 -7.89 -7.11 > -74.3 > 32k -1.92 -4.44 -9.27 -7.94 -1.79 -3.43 -9.45 -8.41 > -78.5 > 64k x x x x x x x x > -85.16 > 128k x x x x x x x x > -87.66 > > > > diff -urN linux-2.4.9-v/fs/pipe.c linux-2.4.9-pipe-new/fs/pipe.c > --- linux-2.4.9-v/fs/pipe.c Sun Aug 12 21:58:52 2001 > +++ linux-2.4.9-pipe-new/fs/pipe.c Tue Oct 9 10:48:15 2001 > @@ -23,6 +23,14 @@ > * -- Julian Bradfield 1999-06-07. > */ > > +#ifdef CONFIG_SMP > +#define IS_SMP (1) > +#else > +#define IS_SMP (0) > +#endif > + > +struct pipe_stat_t pipe_stat; > + > /* Drop the inode semaphore and wait for a pipe event, atomically */ > void pipe_wait(struct inode * inode) > { > @@ -85,30 +93,40 @@ > > /* Read what data is available. */ > ret = -EFAULT; > - while (count > 0 && (size = PIPE_LEN(*inode))) { > - char *pipebuf = PIPE_BASE(*inode) + PIPE_START > (*inode); > - ssize_t chars = PIPE_MAX_RCHUNK(*inode); > - > - if (chars > count) > - chars = count; > - if (chars > size) > - chars = size; > - > - if (copy_to_user(buf, pipebuf, chars)) > - goto out; > + if (count > 0 && (size = PIPE_LEN(*inode))) { > + do { > + char *pipebuf = PIPE_BASE(*inode) + > PIPE_START(*inode); > + ssize_t chars = PIPE_MAX_RCHUNK(*inode); > + > + if (chars > count) > + chars = count; > + if (chars > size) > + chars = size; > + if (IS_SMP && PIPE_ORDER(*inode) && (chars > > PIPE_SEG(*inode))) > + chars = PIPE_SEG(*inode); > + > + if (copy_to_user(buf, pipebuf, chars)) > + goto out; > > - read += chars; > - PIPE_START(*inode) += chars; > - PIPE_START(*inode) &= (PIPE_SIZE - 1); > - PIPE_LEN(*inode) -= chars; > - count -= chars; > - buf += chars; > + read += chars; > + PIPE_START(*inode) += chars; > + PIPE_START(*inode) &= (PIPE_SIZE(*inode) - > 1); > + PIPE_LEN(*inode) -= chars; > + count -= chars; > + buf += chars; > + if ((count <= 0) || (!(size = PIPE_LEN > (*inode)))) > + break; > + if (IS_SMP && PIPE_ORDER(*inode) && > PIPE_WAITING_WRITERS(*inode) && > + !(filp->f_flags & O_NONBLOCK)) > + > wake_up_interruptible_sync(PIPE_WAIT(*inode)); > + > + } while(1); > } > > /* Cache behaviour optimization */ > if (!PIPE_LEN(*inode)) > PIPE_START(*inode) = 0; > - > + > if (count && PIPE_WAITING_WRITERS(*inode) && !(filp->f_flags & > O_NONBLOCK)) { > /* > * We know that we are going to sleep: signal > @@ -187,10 +205,15 @@ > ssize_t chars = PIPE_MAX_WCHUNK(*inode); > > if ((space = PIPE_FREE(*inode)) != 0) { > + pipebuf = PIPE_BASE(*inode) + PIPE_END > (*inode); > + chars = PIPE_MAX_WCHUNK(*inode); > + > if (chars > count) > chars = count; > if (chars > space) > chars = space; > + if (IS_SMP && PIPE_ORDER(*inode) && (chars > > PIPE_SEG(*inode))) > + chars = PIPE_SEG(*inode); > > if (copy_from_user(pipebuf, buf, chars)) > goto out; > @@ -200,6 +223,9 @@ > count -= chars; > buf += chars; > space = PIPE_FREE(*inode); > + if (IS_SMP && PIPE_ORDER(*inode) && (count > > 0) && space && > + PIPE_WAITING_READERS(*inode) && > !(filp->f_flags & O_NONBLOCK)) > + wake_up_interruptible_sync(PIPE_WAIT > (*inode)); > continue; > } > > @@ -231,14 +257,14 @@ > inode->i_ctime = inode->i_mtime = CURRENT_TIME; > mark_inode_dirty(inode); > > -out: > + out: > up(PIPE_SEM(*inode)); > -out_nolock: > + out_nolock: > if (written) > ret = written; > return ret; > > -sigpipe: > + sigpipe: > if (written) > goto out; > up(PIPE_SEM(*inode)); > @@ -309,7 +335,7 @@ > if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode)) { > struct pipe_inode_info *info = inode->i_pipe; > inode->i_pipe = NULL; > - free_page((unsigned long) info->base); > + free_pages((unsigned long) info->base, info->order); > kfree(info); > } else { > wake_up_interruptible(PIPE_WAIT(*inode)); > @@ -443,8 +469,12 @@ > struct inode* pipe_new(struct inode* inode) > { > unsigned long page; > + int pipe_order = pipe_stat.pipe_size_order; > + > + if (pipe_order > MAX_PIPE_ORDER) > + pipe_order = MAX_PIPE_ORDER; > > - page = __get_free_page(GFP_USER); > + page = __get_free_pages(GFP_USER, pipe_order); > if (!page) > return NULL; > > @@ -458,10 +488,11 @@ > PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 0; > PIPE_WAITING_READERS(*inode) = PIPE_WAITING_WRITERS(*inode) = 0; > PIPE_RCOUNTER(*inode) = PIPE_WCOUNTER(*inode) = 1; > + PIPE_ORDER(*inode) = pipe_order; > > return inode; > -fail_page: > - free_page(page); > + fail_page: > + free_pages(page, pipe_order); > return NULL; > } > > @@ -477,12 +508,12 @@ > static struct inode * get_pipe_inode(void) > { > struct inode *inode = get_empty_inode(); > - > if (!inode) > goto fail_inode; > > if(!pipe_new(inode)) > goto fail_iput; > + > PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 1; > inode->i_fop = &rdwr_pipe_fops; > inode->i_sb = pipe_mnt->mnt_sb; > @@ -501,9 +532,9 @@ > inode->i_blksize = PAGE_SIZE; > return inode; > > -fail_iput: > + fail_iput: > iput(inode); > -fail_inode: > + fail_inode: > return NULL; > } > > @@ -572,20 +603,20 @@ > fd[1] = j; > return 0; > > -close_f12_inode_i_j: > + close_f12_inode_i_j: > put_unused_fd(j); > -close_f12_inode_i: > + close_f12_inode_i: > put_unused_fd(i); > -close_f12_inode: > - free_page((unsigned long) PIPE_BASE(*inode)); > + close_f12_inode: > + free_pages((unsigned long) PIPE_BASE(*inode), PIPE_ORDER > (*inode)); > kfree(inode->i_pipe); > inode->i_pipe = NULL; > iput(inode); > -close_f12: > + close_f12: > put_filp(f2); > -close_f1: > + close_f1: > put_filp(f1); > -no_files: > + no_files: > return error; > } > > @@ -631,7 +662,7 @@ > } > > static DECLARE_FSTYPE(pipe_fs_type, "pipefs", pipefs_read_super, > - FS_NOMOUNT|FS_SINGLE); > + FS_NOMOUNT|FS_SINGLE); > > static int __init init_pipe_fs(void) > { > diff -urN linux-2.4.9-v/include/linux/pipe_fs_i.h > linux-2.4.9-pipe-new/include/linux/pipe_fs_i.h > --- linux-2.4.9-v/include/linux/pipe_fs_i.h Wed Apr 25 17:18:23 > 2001 > +++ linux-2.4.9-pipe-new/include/linux/pipe_fs_i.h Tue Oct 9 > 09:35:35 2001 > @@ -2,6 +2,8 @@ > #define _LINUX_PIPE_FS_I_H > > #define PIPEFS_MAGIC 0x50495045 > +#define MAX_PIPE_ORDER 3 > + > struct pipe_inode_info { > wait_queue_head_t wait; > char *base; > @@ -13,12 +15,20 @@ > unsigned int waiting_writers; > unsigned int r_counter; > unsigned int w_counter; > + unsigned int order; > +}; > + > +struct pipe_stat_t{ > + int pipe_size_order; > + int pipe_seg_order; > }; > +extern struct pipe_stat_t pipe_stat; > > /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual > memory allocation, whereas PIPE_BUF makes atomicity guarantees. */ > -#define PIPE_SIZE PAGE_SIZE > +#define PIPE_SIZE(inode) ((1 << PIPE_ORDER(inode)) * PAGE_SIZE) > > +#define PIPE_ORDER(inode) ((inode).i_pipe->order) > #define PIPE_SEM(inode) (&(inode).i_sem) > #define PIPE_WAIT(inode) (&(inode).i_pipe->wait) > #define PIPE_BASE(inode) ((inode).i_pipe->base) > @@ -32,12 +42,13 @@ > #define PIPE_WCOUNTER(inode) ((inode).i_pipe->w_counter) > > #define PIPE_EMPTY(inode) (PIPE_LEN(inode) == 0) > -#define PIPE_FULL(inode) (PIPE_LEN(inode) == PIPE_SIZE) > -#define PIPE_FREE(inode) (PIPE_SIZE - PIPE_LEN(inode)) > -#define PIPE_END(inode) ((PIPE_START(inode) + PIPE_LEN(inode)) & > (PIPE_SIZE-1)) > -#define PIPE_MAX_RCHUNK(inode) (PIPE_SIZE - PIPE_START(inode)) > -#define PIPE_MAX_WCHUNK(inode) (PIPE_SIZE - PIPE_END(inode)) > - > +#define PIPE_FULL(inode) (PIPE_LEN(inode) == PIPE_SIZE(inode)) > +#define PIPE_FREE(inode) (PIPE_SIZE(inode) - PIPE_LEN(inode)) > +#define PIPE_END(inode) ((PIPE_START(inode) + PIPE_LEN(inode)) & > (PIPE_SIZE(inode)-1)) > +#define PIPE_MAX_RCHUNK(inode) (PIPE_SIZE(inode) - > PIPE_START(inode)) > +#define PIPE_MAX_WCHUNK(inode) (PIPE_SIZE(inode) - > PIPE_END(inode)) > +#define PIPE_SEG(inode) ((PIPE_ORDER(inode) > > pipe_stat.pipe_seg_order) ? \ > + (PIPE_SIZE(inode) >> > pipe_stat.pipe_seg_order): PAGE_SIZE) > /* Drop the inode semaphore and wait for a pipe event, atomically */ > void pipe_wait(struct inode * inode); > > diff -urN linux-2.4.9-v/include/linux/sysctl.h > linux-2.4.9-pipe-new/include/linux/sysctl.h > --- linux-2.4.9-v/include/linux/sysctl.h Wed Aug 15 17:21:21 > 2001 > +++ linux-2.4.9-pipe-new/include/linux/sysctl.h Tue Oct 9 > 10:12:48 2001 > @@ -533,6 +533,7 @@ > FS_LEASES=13, /* int: leases enabled */ > FS_DIR_NOTIFY=14, /* int: directory notification enabled > */ > FS_LEASE_TIME=15, /* int: maximum time to wait for a > lease break */ > + FS_PIPE_SIZE=16, /* int: current number of allocated > pages for PIPE */ > }; > > /* CTL_DEBUG names: */ > diff -urN linux-2.4.9-v/kernel/sysctl.c > linux-2.4.9-pipe-new/kernel/sysctl.c > --- linux-2.4.9-v/kernel/sysctl.c Thu Aug 9 19:41:36 2001 > +++ linux-2.4.9-pipe-new/kernel/sysctl.c Mon Oct 8 13:19:46 > 2001 > @@ -304,6 +304,8 @@ > sizeof(int), 0644, NULL, &proc_dointvec}, > {FS_LEASE_TIME, "lease-break-time", &lease_break_time, > sizeof(int), > 0644, NULL, &proc_dointvec}, > + {FS_PIPE_SIZE, "pipe-sz", &pipe_stat, 2*sizeof(int), > + 0644, NULL, &proc_dointvec}, > {0} > }; > > > _______________________________________________ > Lse-tech mailing list > Lse-tech@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/lse-tech > > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Lse-tech] Re: Patch and Performance of larger pipes 2001-10-24 19:39 ` [Lse-tech] Re: Patch and Performance of larger pipes Hubertus Franke @ 2001-10-30 18:31 ` Hubertus Franke 2001-10-30 20:48 ` Manfred Spraul 2001-11-03 17:39 ` Manfred Spraul 0 siblings, 2 replies; 5+ messages in thread From: Hubertus Franke @ 2001-10-30 18:31 UTC (permalink / raw) To: manfred; +Cc: lse-tech, linux-kernel Manfred, here is some more performance measurement and comparision to round up some of the stuff we have been doing. It would be nice if you could make some comments. As usual raw numbers is not everything and there are other issues to consider. Comments ? -- Hubertus ------------------------------------------------------------------------- We measured actual read and write operation interarrival or delay for some of the examples we have been talking about in recent messages. Some of the observed delay between two successive Read or Write for pipe size=32k, are as follows: microseconds R.Compute W.Compute 1. Grep on 50mb file 950 13 2. cat 50mb | wc 850 13 3. cat 50mb | sort 38 14 4. gunzip | tar 55 3000 5. ls -R / | grep almost both are same (forgot the number :-) (*) R.Compute and W.Compute delay are in microseconds As can be seen and as Ken also earlier mentioned, their are typically these 2 cases where either small read/large write or vice versa. We approximated these to 500/0 or 0/500 scenarios and ran the pipeflex benchmark over these (*) R.Size and W.Size are Read & Write transfer size 2-way ----- %imp R.Size W.Size R.Compute W.Compute 2.4.9.pipe Manfred ------ ------ ---------------- ---------- -------------- 512 32k 500 0 1.04 1.04 512 32k 0 500 96.79 83.27 32k 512 500 0 358.75 -12.03 32k 512 0 500 0 0 UP -- %imp R.Size W.Size R.Compute W.Compute 2.4.9.pipe Manfred ------ ------ ------------------- ---------- -------------- 512 32k 500 0 0 1.04 512 32k 0 500 -0.91 7.72 32k 512 500 0 1.09 -78.3 32k 512 0 500 0 0 >From the above numbers it is clear that R.Compute > W.Compute and a large Read Size is giving tremendous performance improvement for our patch on a 2-way machine and no harm on UP. Whereas Manfred's patch is doing 12% degradation on 2-way and 78% degradation on UP. We also tested for one of the scenarios (R. Compute (950) and W.Compute (13)) delay to our pipeflex and kept the same Read and Write transfer size. We got almost the same % improvement (150%). Manfred's patch showed a 53% degration for the grep on UP. -- Hubertus * Hubertus Franke <frankeh@watson.ibm.com> [20011024 15;39]:" > * Kenneth Rozendal <kenroz@us.ibm.com> [20011019 12;28]:" > > Hubertus, > > > > Since the vast majority of all use of pipes involve very small writes > > (commonly one line at a time), it would be useful to see the impact on this > > case. Any solution probably needs to show insignificant degredation in > > this case. The two interesting endpoints are when the reader is faster > > than the writer (pipe mostly empty) and when the writer is faster than the > > reader (pipe mostly full). Most use of pipes will stabilize into one of > > these two cases. > > > > Thanks, > > Ken > > > > > > As requested by Ken, we measured pipes bandwidth > for small writes and reads (32,128,512 bytes) > with different computation time spend either after read/write. > In saturated state leads to the pipe typically > being full or empty. > Here are the results which compares our pipe expansion patch and > Manfred's patch over vanilla kernel when run with pipeflex. > > > As can be seen, our patch does not have any significant impact in > this situations. > Manfred's patch too shows no impact when the pipe is > typically empty, i.e. readers are waiting. > However, in the other case, when the pipe is typically full, i.e > writers are waiting, for small transfer sizes and small delays > on the reader, there is substantial benefit, which however fades > for larger transfer sizes and/or larger read delays. > > In the previous messages, we had shown that our patch actually > improves significantly over vanilla and larger transfer sizes > while Manfred's patch degrades. > > Again, no clear answer to what is the right approach of doing things. > Any thoughts.... > > > -- Hubertus Franke + Rajan Ravindran > > R/W - Read and Write #Bytes over the pipe. > R.Compute - Computation delay between each read > W.Compute - Computation delay between each write. > > 2-way > ----- > Pipe Size (W.Compute=0) > %imp > R/W R.Compute 4k 8k 16k 32k Manfred > 32 10 -1.88 -1.85 -1.99 -2.02 26.28 > 32 100 -0.53 -0.37 -0.28 -0.28 4.54 > 32 1000 -0.02 -0.03 -0.01 -0.02 0.44 > > 128 10 -1.57 -2.17 -2.39 -1.81 15.69 > 128 100 0.03 0.02 -0.02 -0.2 4.18 > 128 1000 -0.05 -0.02 -0.07 -0.04 0.61 > > 512 10 -0.19 -1.41 -1.75 -2.6 0.88 > 512 100 -0.35 -0.16 -0.14 -0.32 4.39 > 512 1000 -0.05 0.18 0.18 0.37 0.64 > > > > Pipe Size (R.Compute=0) > %imp > R/W W.Compute 4k 8k 16k 32k Manfred > 32 10 -1.75 -1.28 -1.16 -0.82 1.84 > 32 100 0.03 -0.16 -0.04 0.14 -0.02 > 32 1000 -0.18 0.01 0.21 0.03 0 > > 128 10 -1.09 -1.54 -2.24 -2.39 1.92 > 128 100 0.52 0.91 1.1 0.98 -0.07 > 128 1000 0.05 0.07 0.08 -0.12 0 > > 512 10 -4.97 -7.09 -7.34 -6.54 3.31 > 512 100 2.07 1.98 1.98 2.18 -0.28 > 512 1000 0.19 0.42 0.23 0.43 -0.02 > > UP > -- > > Pipe Size (W.Compute=0) > %imp > R/W R.Compute 4k 8k 16k 32k Manfred > 32 10 -1.8 -1.33 -1.57 -2.2 29.59 > 32 100 -0.15 -0.12 -0.41 -0.43 4.13 > 32 1000 -0.01 -0.03 -0.04 -0.03 0.44 > > 128 10 0.13 -0.02 -1.83 -2.83 27.76 > 128 100 -0.07 -0.17 -0.61 -0.74 4.05 > 128 1000 -0.02 -0.03 -0.07 -0.07 0.38 > > 512 10 -1.14 -2.51 -4.69 -6.93 24.56 > 512 100 -0.12 -0.45 -1 -1.44 3.6 > 512 1000 0 -0.04 -0.11 -0.13 0.45 > > > > Pipe Size (R.Compute=0) > %imp > R/W W.Compute 4k 8k 16k 32k Manfred > 32 10 -0.69 -0.67 -1.7 -0.55 0.19 > 32 100 -0.32 -0.25 -0.17 -0.1 0.17 > 32 1000 -0.1 -2.14 -0.11 -0.05 0.03 > > 128 10 -1.87 -0.71 -0.67 -0.43 -0.67 > 128 100 -0.14 -0.14 -0.22 -0.11 -0.02 > 128 1000 -0.02 -0.4 -0.03 -0.03 -0.07 > > 512 10 -0.2 -0.13 -1.45 -0.78 -1.67 > 512 100 -0.06 -0.21 -0.07 -0.14 -0.11 > 512 1000 0 -0.11 -0.03 -0.19 -0.01 > > > > > > > Ken Rozendal > > STSM - Linux kernel technology lead > > IBM Linux Technology Center > > (512)-794-1163, IBM Tie-Line 450-9015 > > kenroz@us.ibm.com > > > > > > > > > > Hubertus Franke <frankeh@watson.ibm.com>@lists.sourceforge.net on > > 10/19/2001 08:52:51 AM > > > > Please respond to frankeh@watson.ibm.com > > > > Sent by: lse-tech-admin@lists.sourceforge.net > > > > > > To: Manfred Spraul <manfred@colorfullife.com> > > cc: linux-kernel@vger.kernel.org, lse-tech@lists.sourceforge.net > > Subject: [Lse-tech] Re: Patch and Performance of larger pipes > > > > > > > > Well we did for all the 3 benchmarks.... > > > > * Manfred Spraul <manfred@colorfullife.com> [20011018 14;07]:" > > > Could you test the attached singlecopy patches? > > > > > > with bw_pipe, > > > * on UP, up to +100%. > > > * on SMP with busy cpus, up to +100% > > > * on SMP with idle cpus a performance drop due to increased cache > > > trashing. Probably the scheduler should keep both bw_pipe processes on > > > the same cpu. > > > > > > I've sent patch-pgw to Linus for inclusion, since it's needed to fix the > > > elf coredump deadlock. > > > > > > patch-kiopipe must wait until 2.5, because it changes the behaviour of > > > pipe_write with partial reads. > > > > > > -- > > > Manfred > > > > > <<< Manfred's patch cout out >>> > > > > > > > > Ok, at the request by Manfred Spraul we also ran his <single-copy> > > patch. Manfred patch has applied over 2.4.13-pre13 and the results are > > compared > > over its base vanilla kernel. Our numbers still are %-improvements numbers > > of patched 2.4.9 kernel vs. 2.4.9 vanilla. > > Manfred's numbers are added as an additional column. > > > > << Bottom-line >> > > > > Our patch does better for <Grep> and <Pipeflex> benchmark and > > <LMBench> on low transfer sizes for large Pipe-Buffers. > > This is only relevant for SMP systems as we have enabled the patch > > only for SMP. > > > > Manfred's patch does better for <LMBench> and beats our patch across > > configurations. But it lacks even vanilla for more realistic apps. > > The same observation holds for UP. > > > > We have not measured CPU utilization etc. > > As stated in my earlier message, bw_pipe doesn't have a lot of real > > applicability, but I am willing to be re-educated here. > > > > -- Hubertus > > > > PIPE: Buffer Expansion > > ---------------------- > > > > In this we will report on some experimentation to improve Linux pipe > > performance. There are two basic parameters that govern the Linux pipe > > implementation. > > (a) PIPE_SIZE is the size of the pipe buffer. > > (b) PIPE_BUF is the maximum number of bytes an application > > can write atomically to the pipe. > > > > In the current implementation size of pipe buffer is PAGE_SIZE (most > > architectures that is 4kB, and the PIPE_BUF is fixed to 4kB (and for > > ARM=PAGE_SIZE). > > > > We wanted to experiment with larger pipe buffer support and higher > > concurrency of read and writes. Therefore we experimented with the > > following items: > > > > (A) expanding the pipe buffer size from 1 page to 2,4,8 pages. > > > > (B) improving the pipe's concurrency of read and write by introducing > > intermittent activation of pending readers/writers rather than at > > the end of a pipe transaction (read/write). The PIPE_BUF > > atomicity constraint is still observed. We therefore introduce > > the term of a PIPE_SEG which is a multiple of the PAGE_SIZE and > > determines when to wake up pending readers and writers. > > > > Consider the pipe buffer size to be 32k. The space available to > > write on the pipe is 32k and the data which is coming to be > > written onto the pipe is also 32k. By keeping the segment size > > as 4k, write the first 4k of the total 32k data instead of > > writing the entire 32k data, and inform the reader process that > > some data is there to be read, and the writer process proceeds > > with the next 4k. By that time reader process starts reading > > the available data. Intuitively this should create > > more concurrency. > > > > Throughout this experimentation, we kept the PIPE_BUF (atomicity > > guarantee) constant at 4kB. > > > > Benchmarks > > ---------- > > > > The benchmarks we ran for measuring the performance of pipes are > > LMBench, Grep, and Pipeflex. The description of these are below. > > While LMBench is a widely used OS-Benchmark, we found that Grep and > > Pipeflex model more real applications. All are descripted in more > > detail below. All applications use different data transfer sizes > > aka chunk sizes shown as TS. We report on the two aspects of our > > implementation, i.e. larger pipes and intermittent activations > > (PIPE_SEG) which is always 4k. All results are shown as % improvement > > over the baseline kernel (2.4.9) and all these benchmarks are run on a > > 2-way Pentium II, 333Mhz machine. > > > > Results Summary: > > ================ > > > > UP + 1-way SMP: > > --------------- > > Neither (A) nor (A)+(B) showed any improvements. Instead degradations > > of up to 30% are observed. Obviously our approach/patch does not > > make any sense on the 1-way systems. > > > > N-way SMP: > > ---------- > > > > 1. Increasing the pipe buffer size (A) increasingly improves the > > performance of the Grep benchmark by upto 165% for size 32kB. > > However, Grep does not show any added benefit nor > > degradation utilizing (A)+(B), i.e, expanding the pipe buffer > > size AND introducing the segment size=4kB. > > > > 2. For LMBench, (A) alone shows some improvements for small transfer > > sizes (TS<PIPE_SIZE). For TS>>PIPE_SIZE we observe degradation. > > Introducing (A)+(B) shows even better improvements for small TS > > with very small degradations for larger TS. > > > > 3. For pipeflex (A) provides increasing benefits with upto 358% > > improvements, without any loss at the low end. When introducing > > (A)+(B), the benefits drops but are still substantial. > > > > Based on the results it is clear that expansion of PIPE_SIZE AND > > PIPE_SEG introduction gives better performance for some scenarios. > > > > > > Grep > > ---- > > > > This benchmark measures the time taken to grep for some unexisting > > pattern on a 50mb file. ie. cat 50mbfile | grep "$$$$". We assume a > > warm file cache. > > > > LMBench > > ------- > > > > LMBench provides a tool to measure the bandwidth of the pipe > > (bw_pipe). bw_pipe creates pipes between two processes and moves 10MB > > through the pipe in 64KB chunks. We altered that code by providing the > > chunk size as a variable input parameter. ie. bw_pipe [2,4,...,32] > > > > Pipeflex > > -------- > > > > As LMBench does continuous read and write over the pipe in a > > synchronous manner (which is not the case in real life), we studied > > some test cases which uses pipes(grep, wc, sort, gunzip, ..), and > > based on that we have written this pipeflex benchmark. > > > > Here a write process writes smaller chunks continuously and the reader > > process generates a number between [0.5*r .. 1.5*r] microseconds, and > > spends that time for computation after each pipe reads. > > > > A parent process clones 'c' child processes and 'c/2' pipes such that > > 2 processes shares one pipe. > > ie. pipeflex -c 2 -t 20 -r 500 -s 4 > > > > c : number of children/threads to launch (should be EVEN) > > t : time for which each run of the test should be performed. > > r : microseconds spend in computation after each pipe reads. > > s : data to transfer over pipe in Kilo bytes. > > > > > > Dynamically assigning values for PIPE_SIZE and PIPE_SEG > > ------------------------------------------------------- > > > > In our current implementation, the size of PIPE_SIZE and PIPE_SEG can > > be changed dynamically by writing the values into the newly created > > /proc/sys/fs/pipe-sz file through a string having the following > > format: > > > > Po So > > > > where Po is the Pipe size order > > and So is the Segment size order. > > > > Pipe size will be calculated as PIPE_SIZE = (1 << Po) * PAGE_SIZE. > > Segment size will be calculated as (PIPE_SIZE >> So). > > > > Similarly 'Po' and 'So' can be read through the same proc file. > > > > * The notation we use in tables for PIPE_SIZE and PIPE_SEG are PS and > > SS respectively and TS is the Transfer Size over pipe. > > > > 2-way (% improvement) Results > > ============================= > > > > Grep > > ---- > > > > PS (A) (A)+(B) Manfred > > -- --- ------- ------- > > 4k -0.87 -0.95 39.9 > > 8k 50.84 50.12 > > 16k 107.97 115.86 > > 32k 165.25 164.14 > > > > > > LMBench > > ------- > > (A) (A)+(B) > > > > --- ------- > > > > > > PS PS > > > > TS 4k 8k 16k 32k 4k 8k 16k 32k > > Manfred > > -- -- -- --- --- -- -- --- --- > > ------- > > 2k -0.3 3.26 4.25 3.83 -0.3 2.98 4.25 4.04 > > 54.1 > > 4k -2.18 18.97 18.59 18.59 -2.18 18.59 18.59 18.59 > > 21.0 > > 6k 0.34 13.08 32.7 49.57 0.3 35.63 39.76 55.94 > > 69.2 > > 8k 0.14 3.02 0 -0.82 13.87 31.59 50.82 75.27 > > 63.2 > > 12k 0.34 -24.09 -18.74 -12.57 0.34 4.4 -14.86 8.23 > > 38.3 > > 16k 1.47 -8.88 -14.16 -16.03 1.4 14.42 9.48 13.86 > > 37.5 > > 24k 1.17 -13.9 1.65 -23.59 1.17 1.65 -2.72 1.2 > > 31.2 > > 32k 0.66 -14.77 -19.83 -25.63 0.66 -3.2 -6.59 -2.92 > > 27.2 > > 64k x x x x x x x x > > 22.84 > > 128k x x x x x x x x > > 29.7 > > > > > > Pipeflex > > -------- > > > > (A) (A)+(B) > > --- ------- > > > > PS PS > > TS 4k 8k 16k 32k 4k 8k 16k 32k > > Manfred > > -- -- -- --- --- -- -- --- --- > > 2k 0.00 0.00 -0.27 -0.27 0.00 -0.27 -0.27 -0.27 > > -24.1 > > 4k 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 > > -42.0 > > 6k 1.61 -1.82 11.46 10.28 1.61 -9.53 9.53 6.75 > > -10.86 > > 8k -2.00 46.20 46.31 46.31 -2.00 -11.08 7.17 23.73 > > -15.9 > > 12k -2.93 54.13 64.58 93.31 -2.93 51.62 46.08 84.22 > > -14.9 > > 16k -3.34 49.95 163.09 162.67 -3.34 51.82 45.57 85.92 > > -14.4 > > 24k -3.56 50.37 135.50 183.46 -3.56 49.95 134.97 144.40 > > -15.9 > > 32k -1.40 54.99 143.29 358.75 -1.40 55.75 142.32 147.37 > > -17.7 > > 64k x x x x x x x x > > -15.01 > > 128k x x x x x x x x > > -15.14 > > > > > > 1-way (% improvement) Results > > ============================= > > > > Grep > > ---- > > > > PS (A) (A)+(B) Manfred > > -- --- ------- ------- > > 4k -0.47 -0.47 -49.78 > > 8k 1.9 -2.73 > > 16k -2.73 -2.73 > > 32k 1.9 -2.73 > > > > > > > > LMBench > > ------- > > (A) (A)+(B) > > --- ------- > > > > PS PS > > TS 4k 8k 16k 32k 4k 8k 16k 32k > > Manfred > > -- -- -- --- --- -- -- --- --- > > ------- > > 2k 0.49 4.42 -3.88 -10.13 0.49 11.02 -7.68 -12.06 > > 5.91 > > 4k -0.5 -1.08 -22.17 -8.6 -0.5 -0.95 -18.65 -4.86 > > 24.28 > > 6k 3.73 -19.03 -24.23 -18.56 3.73 -15.85 -24.68 -12.44 > > 55.17 > > 8k 0.82 -33.43 -31.92 -30.19 0.82 -34.38 -25.41 -12.81 > > 35.34 > > 12k 1.39 -24.06 -30.67 -27.88 1.39 -24.43 -29.79 -27 > > 20.39 > > 16k -0.87 -29.16 -31.27 -29.73 -0.87 -28.53 -31.97 -28.97 > > 24.8 > > 24k 0.16 -28.79 -31.87 -28.37 0.16 -28.16 -31.61 -28.66 > > 32.72 > > 32k 0.35 -28.91 -30.73 -27.23 0.35 -28.77 -31.6 -28.77 > > 34.89 > > 64k x x x x x x x x > > 38.7 > > 128k x x x x x x x x > > 41.6 > > > > Pipeflex > > -------- > > > > (A) (A)+(B) > > --- ------- > > > > PS PS > > TS 4k 8k 16k 32k 4k 8k 16k 32k > > Manfred > > -- -- -- --- --- -- -- --- --- > > ------- > > 2k 0.00 -0.54 -0.80 -1.07 0.00 -0.54 -0.80 -1.07 > > -23.66 > > 4k -0.14 -0.69 -1.80 -2.21 -0.14 -1.10 -1.80 -2.49 > > -41.97 > > 6k -0.19 -0.19 -2.41 -2.02 -0.19 -0.19 -2.12 -1.16 > > -22.09 > > 8k -0.30 -1.86 -6.41 -6.41 -0.30 -1.19 -3.80 -2.61 > > -39.97 > > 12k -0.33 -1.43 -4.56 -4.01 -0.33 -1.43 -3.84 -3.51 > > -55.71 > > 16k -0.18 -1.77 -4.47 -4.56 -0.18 -1.15 -4.78 -3.85 > > -64.37 > > 24k -0.37 -2.21 -6.94 -5.26 -0.37 -1.51 -6.07 -4.89 > > -72.98 > > 32k -0.42 -2.98 -7.12 -5.18 -0.42 -1.75 -7.06 -5.77 > > -77.19 > > 64k x x x x x x x x > > -82.57 > > 128k x x x x x x x x > > -84.91 > > > > UP (% improvement) Results > > ========================== > > > > Grep > > ---- > > > > PS (A) (A)+(B) Manfred > > -- --- ------- ------- > > 4k -0.53 1.61 -53.49 > > 8k -2.58 -1.56 > > 16k -4.55 -4.06 > > 32k -3.08 -4.06 > > > > > > LMBench > > ------- > > (A) (A)+(B) > > --- ------- > > > > PS PS > > TS 4k 8k 16k 32k 4k 8k 16k 32k > > Manfred > > -- -- -- --- --- -- -- --- --- > > ------- > > 2k 7.38 1.17 -15.28 -18.07 4.18 -0.36 -14.32 -20.55 > > 16.35 > > 4k -1.73 -0.5 -31.7 -26.94 -1.21 5.61 -21.75 -5.17 > > 20.58 > > 6k -0.3 -22.33 -26.78 -23.36 -0.9 -17.31 -29.61 -19.5 > > 73.06 > > 8k 7.8 -35 -33.75 -30.65 1.71 -37.11 -29.45 -18.03 > > 30.43 > > 12k -1.09 -25.99 -36.7 -35.77 0.13 -27.76 -35.56 -34.21 > > 13.78 > > 16k 0.08 -31.39 -35.37 -34.28 1.2 -30.93 -36.18 -34.18 > > 17.47 > > 24k 0.42 -32.06 -36.15 -34.65 0.63 -32.28 -36.82 -34.98 > > 22.03 > > 32k 0.82 -31.52 -35.71 -33.41 1.8 -32.11 -36.49 -34.52 > > 24.87 > > 64k x x x x x x x x > > 26.66 > > 128k x x x x x x x x > > 41.27 > > > > > > Pipeflex > > -------- > > > > (A) (A)+(B) > > --- ------- > > > > PS PS > > TS 4k 8k 16k 32k 4k 8k 16k 32k > > Manfred > > -- -- -- --- --- -- -- --- --- > > ------- > > 2k -0.27 -0.27 -0.80 -1.06 -0.27 -0.27 -0.80 -1.06 > > -24.4 > > 4k -0.27 -0.68 -1.77 -2.31 -0.14 -0.54 -1.63 -2.18 > > -42.3 > > 6k -0.66 -0.94 -3.85 -3.94 -0.47 -0.66 -2.63 -1.97 > > -22.9 > > 8k -0.58 -1.96 -6.88 -6.88 -0.58 -1.30 -4.49 -3.48 > > -40.5 > > 12k -1.00 -2.16 -5.59 -5.59 -0.84 -1.79 -4.75 -4.54 > > -56.7 > > 16k -1.22 -2.40 -6.02 -6.18 -1.14 -2.10 -6.06 -5.34 > > -65.4 > > 24k -1.50 -3.41 -8.68 -7.23 -1.72 -2.76 -7.89 -7.11 > > -74.3 > > 32k -1.92 -4.44 -9.27 -7.94 -1.79 -3.43 -9.45 -8.41 > > -78.5 > > 64k x x x x x x x x > > -85.16 > > 128k x x x x x x x x > > -87.66 > > > > > > > > diff -urN linux-2.4.9-v/fs/pipe.c linux-2.4.9-pipe-new/fs/pipe.c > > --- linux-2.4.9-v/fs/pipe.c Sun Aug 12 21:58:52 2001 > > +++ linux-2.4.9-pipe-new/fs/pipe.c Tue Oct 9 10:48:15 2001 > > @@ -23,6 +23,14 @@ > > * -- Julian Bradfield 1999-06-07. > > */ > > > > +#ifdef CONFIG_SMP > > +#define IS_SMP (1) > > +#else > > +#define IS_SMP (0) > > +#endif > > + > > +struct pipe_stat_t pipe_stat; > > + > > /* Drop the inode semaphore and wait for a pipe event, atomically */ > > void pipe_wait(struct inode * inode) > > { > > @@ -85,30 +93,40 @@ > > > > /* Read what data is available. */ > > ret = -EFAULT; > > - while (count > 0 && (size = PIPE_LEN(*inode))) { > > - char *pipebuf = PIPE_BASE(*inode) + PIPE_START > > (*inode); > > - ssize_t chars = PIPE_MAX_RCHUNK(*inode); > > - > > - if (chars > count) > > - chars = count; > > - if (chars > size) > > - chars = size; > > - > > - if (copy_to_user(buf, pipebuf, chars)) > > - goto out; > > + if (count > 0 && (size = PIPE_LEN(*inode))) { > > + do { > > + char *pipebuf = PIPE_BASE(*inode) + > > PIPE_START(*inode); > > + ssize_t chars = PIPE_MAX_RCHUNK(*inode); > > + > > + if (chars > count) > > + chars = count; > > + if (chars > size) > > + chars = size; > > + if (IS_SMP && PIPE_ORDER(*inode) && (chars > > > PIPE_SEG(*inode))) > > + chars = PIPE_SEG(*inode); > > + > > + if (copy_to_user(buf, pipebuf, chars)) > > + goto out; > > > > - read += chars; > > - PIPE_START(*inode) += chars; > > - PIPE_START(*inode) &= (PIPE_SIZE - 1); > > - PIPE_LEN(*inode) -= chars; > > - count -= chars; > > - buf += chars; > > + read += chars; > > + PIPE_START(*inode) += chars; > > + PIPE_START(*inode) &= (PIPE_SIZE(*inode) - > > 1); > > + PIPE_LEN(*inode) -= chars; > > + count -= chars; > > + buf += chars; > > + if ((count <= 0) || (!(size = PIPE_LEN > > (*inode)))) > > + break; > > + if (IS_SMP && PIPE_ORDER(*inode) && > > PIPE_WAITING_WRITERS(*inode) && > > + !(filp->f_flags & O_NONBLOCK)) > > + > > wake_up_interruptible_sync(PIPE_WAIT(*inode)); > > + > > + } while(1); > > } > > > > /* Cache behaviour optimization */ > > if (!PIPE_LEN(*inode)) > > PIPE_START(*inode) = 0; > > - > > + > > if (count && PIPE_WAITING_WRITERS(*inode) && !(filp->f_flags & > > O_NONBLOCK)) { > > /* > > * We know that we are going to sleep: signal > > @@ -187,10 +205,15 @@ > > ssize_t chars = PIPE_MAX_WCHUNK(*inode); > > > > if ((space = PIPE_FREE(*inode)) != 0) { > > + pipebuf = PIPE_BASE(*inode) + PIPE_END > > (*inode); > > + chars = PIPE_MAX_WCHUNK(*inode); > > + > > if (chars > count) > > chars = count; > > if (chars > space) > > chars = space; > > + if (IS_SMP && PIPE_ORDER(*inode) && (chars > > > PIPE_SEG(*inode))) > > + chars = PIPE_SEG(*inode); > > > > if (copy_from_user(pipebuf, buf, chars)) > > goto out; > > @@ -200,6 +223,9 @@ > > count -= chars; > > buf += chars; > > space = PIPE_FREE(*inode); > > + if (IS_SMP && PIPE_ORDER(*inode) && (count > > > 0) && space && > > + PIPE_WAITING_READERS(*inode) && > > !(filp->f_flags & O_NONBLOCK)) > > + wake_up_interruptible_sync(PIPE_WAIT > > (*inode)); > > continue; > > } > > > > @@ -231,14 +257,14 @@ > > inode->i_ctime = inode->i_mtime = CURRENT_TIME; > > mark_inode_dirty(inode); > > > > -out: > > + out: > > up(PIPE_SEM(*inode)); > > -out_nolock: > > + out_nolock: > > if (written) > > ret = written; > > return ret; > > > > -sigpipe: > > + sigpipe: > > if (written) > > goto out; > > up(PIPE_SEM(*inode)); > > @@ -309,7 +335,7 @@ > > if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode)) { > > struct pipe_inode_info *info = inode->i_pipe; > > inode->i_pipe = NULL; > > - free_page((unsigned long) info->base); > > + free_pages((unsigned long) info->base, info->order); > > kfree(info); > > } else { > > wake_up_interruptible(PIPE_WAIT(*inode)); > > @@ -443,8 +469,12 @@ > > struct inode* pipe_new(struct inode* inode) > > { > > unsigned long page; > > + int pipe_order = pipe_stat.pipe_size_order; > > + > > + if (pipe_order > MAX_PIPE_ORDER) > > + pipe_order = MAX_PIPE_ORDER; > > > > - page = __get_free_page(GFP_USER); > > + page = __get_free_pages(GFP_USER, pipe_order); > > if (!page) > > return NULL; > > > > @@ -458,10 +488,11 @@ > > PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 0; > > PIPE_WAITING_READERS(*inode) = PIPE_WAITING_WRITERS(*inode) = 0; > > PIPE_RCOUNTER(*inode) = PIPE_WCOUNTER(*inode) = 1; > > + PIPE_ORDER(*inode) = pipe_order; > > > > return inode; > > -fail_page: > > - free_page(page); > > + fail_page: > > + free_pages(page, pipe_order); > > return NULL; > > } > > > > @@ -477,12 +508,12 @@ > > static struct inode * get_pipe_inode(void) > > { > > struct inode *inode = get_empty_inode(); > > - > > if (!inode) > > goto fail_inode; > > > > if(!pipe_new(inode)) > > goto fail_iput; > > + > > PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 1; > > inode->i_fop = &rdwr_pipe_fops; > > inode->i_sb = pipe_mnt->mnt_sb; > > @@ -501,9 +532,9 @@ > > inode->i_blksize = PAGE_SIZE; > > return inode; > > > > -fail_iput: > > + fail_iput: > > iput(inode); > > -fail_inode: > > + fail_inode: > > return NULL; > > } > > > > @@ -572,20 +603,20 @@ > > fd[1] = j; > > return 0; > > > > -close_f12_inode_i_j: > > + close_f12_inode_i_j: > > put_unused_fd(j); > > -close_f12_inode_i: > > + close_f12_inode_i: > > put_unused_fd(i); > > -close_f12_inode: > > - free_page((unsigned long) PIPE_BASE(*inode)); > > + close_f12_inode: > > + free_pages((unsigned long) PIPE_BASE(*inode), PIPE_ORDER > > (*inode)); > > kfree(inode->i_pipe); > > inode->i_pipe = NULL; > > iput(inode); > > -close_f12: > > + close_f12: > > put_filp(f2); > > -close_f1: > > + close_f1: > > put_filp(f1); > > -no_files: > > + no_files: > > return error; > > } > > > > @@ -631,7 +662,7 @@ > > } > > > > static DECLARE_FSTYPE(pipe_fs_type, "pipefs", pipefs_read_super, > > - FS_NOMOUNT|FS_SINGLE); > > + FS_NOMOUNT|FS_SINGLE); > > > > static int __init init_pipe_fs(void) > > { > > diff -urN linux-2.4.9-v/include/linux/pipe_fs_i.h > > linux-2.4.9-pipe-new/include/linux/pipe_fs_i.h > > --- linux-2.4.9-v/include/linux/pipe_fs_i.h Wed Apr 25 17:18:23 > > 2001 > > +++ linux-2.4.9-pipe-new/include/linux/pipe_fs_i.h Tue Oct 9 > > 09:35:35 2001 > > @@ -2,6 +2,8 @@ > > #define _LINUX_PIPE_FS_I_H > > > > #define PIPEFS_MAGIC 0x50495045 > > +#define MAX_PIPE_ORDER 3 > > + > > struct pipe_inode_info { > > wait_queue_head_t wait; > > char *base; > > @@ -13,12 +15,20 @@ > > unsigned int waiting_writers; > > unsigned int r_counter; > > unsigned int w_counter; > > + unsigned int order; > > +}; > > + > > +struct pipe_stat_t{ > > + int pipe_size_order; > > + int pipe_seg_order; > > }; > > +extern struct pipe_stat_t pipe_stat; > > > > /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual > > memory allocation, whereas PIPE_BUF makes atomicity guarantees. */ > > -#define PIPE_SIZE PAGE_SIZE > > +#define PIPE_SIZE(inode) ((1 << PIPE_ORDER(inode)) * PAGE_SIZE) > > > > +#define PIPE_ORDER(inode) ((inode).i_pipe->order) > > #define PIPE_SEM(inode) (&(inode).i_sem) > > #define PIPE_WAIT(inode) (&(inode).i_pipe->wait) > > #define PIPE_BASE(inode) ((inode).i_pipe->base) > > @@ -32,12 +42,13 @@ > > #define PIPE_WCOUNTER(inode) ((inode).i_pipe->w_counter) > > > > #define PIPE_EMPTY(inode) (PIPE_LEN(inode) == 0) > > -#define PIPE_FULL(inode) (PIPE_LEN(inode) == PIPE_SIZE) > > -#define PIPE_FREE(inode) (PIPE_SIZE - PIPE_LEN(inode)) > > -#define PIPE_END(inode) ((PIPE_START(inode) + PIPE_LEN(inode)) & > > (PIPE_SIZE-1)) > > -#define PIPE_MAX_RCHUNK(inode) (PIPE_SIZE - PIPE_START(inode)) > > -#define PIPE_MAX_WCHUNK(inode) (PIPE_SIZE - PIPE_END(inode)) > > - > > +#define PIPE_FULL(inode) (PIPE_LEN(inode) == PIPE_SIZE(inode)) > > +#define PIPE_FREE(inode) (PIPE_SIZE(inode) - PIPE_LEN(inode)) > > +#define PIPE_END(inode) ((PIPE_START(inode) + PIPE_LEN(inode)) & > > (PIPE_SIZE(inode)-1)) > > +#define PIPE_MAX_RCHUNK(inode) (PIPE_SIZE(inode) - > > PIPE_START(inode)) > > +#define PIPE_MAX_WCHUNK(inode) (PIPE_SIZE(inode) - > > PIPE_END(inode)) > > +#define PIPE_SEG(inode) ((PIPE_ORDER(inode) > > > pipe_stat.pipe_seg_order) ? \ > > + (PIPE_SIZE(inode) >> > > pipe_stat.pipe_seg_order): PAGE_SIZE) > > /* Drop the inode semaphore and wait for a pipe event, atomically */ > > void pipe_wait(struct inode * inode); > > > > diff -urN linux-2.4.9-v/include/linux/sysctl.h > > linux-2.4.9-pipe-new/include/linux/sysctl.h > > --- linux-2.4.9-v/include/linux/sysctl.h Wed Aug 15 17:21:21 > > 2001 > > +++ linux-2.4.9-pipe-new/include/linux/sysctl.h Tue Oct 9 > > 10:12:48 2001 > > @@ -533,6 +533,7 @@ > > FS_LEASES=13, /* int: leases enabled */ > > FS_DIR_NOTIFY=14, /* int: directory notification enabled > > */ > > FS_LEASE_TIME=15, /* int: maximum time to wait for a > > lease break */ > > + FS_PIPE_SIZE=16, /* int: current number of allocated > > pages for PIPE */ > > }; > > > > /* CTL_DEBUG names: */ > > diff -urN linux-2.4.9-v/kernel/sysctl.c > > linux-2.4.9-pipe-new/kernel/sysctl.c > > --- linux-2.4.9-v/kernel/sysctl.c Thu Aug 9 19:41:36 2001 > > +++ linux-2.4.9-pipe-new/kernel/sysctl.c Mon Oct 8 13:19:46 > > 2001 > > @@ -304,6 +304,8 @@ > > sizeof(int), 0644, NULL, &proc_dointvec}, > > {FS_LEASE_TIME, "lease-break-time", &lease_break_time, > > sizeof(int), > > 0644, NULL, &proc_dointvec}, > > + {FS_PIPE_SIZE, "pipe-sz", &pipe_stat, 2*sizeof(int), > > + 0644, NULL, &proc_dointvec}, > > {0} > > }; > > > > > > _______________________________________________ > > Lse-tech mailing list > > Lse-tech@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/lse-tech > > > > > > _______________________________________________ > Lse-tech mailing list > Lse-tech@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/lse-tech ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Lse-tech] Re: Patch and Performance of larger pipes 2001-10-30 18:31 ` Hubertus Franke @ 2001-10-30 20:48 ` Manfred Spraul 2001-11-03 17:39 ` Manfred Spraul 1 sibling, 0 replies; 5+ messages in thread From: Manfred Spraul @ 2001-10-30 20:48 UTC (permalink / raw) To: Hubertus Franke; +Cc: lse-tech, linux-kernel Hubertus Franke wrote: > > Manfred, here is some more performance measurement and comparision > to round up some of the stuff we have been doing. > It would be nice if you could make some comments. As usual raw numbers > is not everything and there are other issues to consider. > Comments ? > I'm that much interested at SMP performance right now - most of the SMP problems are bad interactions with the scheduler. The current scheduler and the pipe implementation are "optimized" for each other, e.g. wake_up_sync() is IIRC exclusively used by pipes. > > UP > -- > %imp > R.Size W.Size R.Compute W.Compute 2.4.9.pipe Manfred > ------ ------ ------------------- ---------- -------------- > 512 32k 500 0 0 1.04 > 512 32k 0 500 -0.91 7.72 > > 32k 512 500 0 1.09 -78.3 > 32k 512 0 500 0 0 > I'll try to check that one ASAP. An uniprocessor performance degration points to an implementation bug in my code. -- Manfred ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Lse-tech] Re: Patch and Performance of larger pipes 2001-10-30 18:31 ` Hubertus Franke 2001-10-30 20:48 ` Manfred Spraul @ 2001-11-03 17:39 ` Manfred Spraul 2001-11-05 14:11 ` Hubertus Franke 1 sibling, 1 reply; 5+ messages in thread From: Manfred Spraul @ 2001-11-03 17:39 UTC (permalink / raw) To: Hubertus Franke; +Cc: lse-tech, linux-kernel Hubertus Franke wrote: > 32k 512 500 0 1.09 -78.3 I understand the slowdown, but 78% are too large. With my patch applied, the read syscall probably returns after 4608 bytes instead of all 32 kB. Could you check that you don't delay after every syscall, but only after 32 kB are read? > > Whereas Manfred's patch is doing 12% degradation on 2-way and 78% > degradation on UP. > I found the problem: The current code does syscall coalescing. On UP, I get <<<<<<<< $dd if=/dev/zero bs=4096 count=20000 | dd bs=1M of=/dev/null 20000+0 records in 20000+0 records out 78+1 records in 78+1 records out $dd if=/dev/zero bs=4096 count=20000 | dd bs=1M of=/dev/null 20000+0 records in 20000+0 records out 77+2 records in 77+2 records out <<<<<<<< [ok, it it SMP, but the 2nd cpu executes 'for(;;);'] Only 80 read syscalls are needed. With my patch applied, I'd get around 10000 syscalls. I haven't found a simple way to fix it yet, probably I must wait until the cache flushing functions are cleaned up. -- Manfred ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Lse-tech] Re: Patch and Performance of larger pipes 2001-11-03 17:39 ` Manfred Spraul @ 2001-11-05 14:11 ` Hubertus Franke 0 siblings, 0 replies; 5+ messages in thread From: Hubertus Franke @ 2001-11-05 14:11 UTC (permalink / raw) To: Manfred Spraul; +Cc: lse-tech, linux-kernel * Manfred Spraul <manfred@colorfullife.com> [20011103 12;39]:" > Hubertus Franke wrote: > > 32k 512 500 0 1.09 -78.3 > > I understand the slowdown, but 78% are too large. > With my patch applied, the read syscall probably returns after 4608 > bytes instead of all 32 kB. Could you check that you don't delay after > every syscall, but only after 32 kB are read? You are right on the money. 4608 every read call..... Now we ran also our patch terms out we also don't return right on 32KB, but dependent on the pipe-size return more than 4608. Even on vanilla, it seems the blocking read semantics are wait for at least 1 byte and then return as much as you can. We are running somemore experiments now to see what exactly is going on. > > > > > Whereas Manfred's patch is doing 12% degradation on 2-way and 78% > > degradation on UP. > > > I found the problem: > The current code does syscall coalescing. > > On UP, I get > <<<<<<<< > $dd if=/dev/zero bs=4096 count=20000 | dd bs=1M of=/dev/null > 20000+0 records in > 20000+0 records out > 78+1 records in > 78+1 records out > $dd if=/dev/zero bs=4096 count=20000 | dd bs=1M of=/dev/null > 20000+0 records in > 20000+0 records out > 77+2 records in > 77+2 records out > <<<<<<<< [ok, it it SMP, but the 2nd cpu executes 'for(;;);'] > Only 80 read syscalls are needed. With my patch applied, I'd get around > 10000 syscalls. > > I haven't found a simple way to fix it yet, probably I must wait until > the cache flushing functions are cleaned up. > -- > Manfred Let's first agree exactly on the read semantics that we want to see ? Than let's keep comparing where things are heading to see what makes the most sense. > > _______________________________________________ > Lse-tech mailing list > Lse-tech@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/lse-tech ^ permalink raw reply [flat|nested] 5+ messages in thread
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Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2001-10-24 19:39 ` [Lse-tech] Re: Patch and Performance of larger pipes Hubertus Franke
2001-10-30 18:31 ` Hubertus Franke
2001-10-30 20:48 ` Manfred Spraul
2001-11-03 17:39 ` Manfred Spraul
2001-11-05 14:11 ` Hubertus Franke
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