Re: [PATCH 0/1] mm, shmem: map few pages around fault address if they are in page cache

[Ning Qu <quning@gmail.com>]

Yes, I am using the iozone -i 0 -i 1. Let me try the most simple test
as you mentioned.
Best wishes,
-- 
Ning Qu


On Fri, Feb 28, 2014 at 5:41 PM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Fri, 28 Feb 2014 16:35:16 -0800 Ning Qu <quning@gmail.com> wrote:
>
>> Sorry about my fault about the experiments, here is the real one.
>>
>> Btw, apparently, there are still some questions about the results and
>> I will sync with Kirill about his test command line.
>>
>> Below is just some simple experiment numbers from this patch, let me know if
>> you would like more:
>>
>> Tested on Xeon machine with 64GiB of RAM, using the current default fault
>> order 4.
>>
>> Sequential access 8GiB file
>>                         Baseline        with-patch
>> 1 thread
>>     minor fault         8,389,052    4,456,530
>>     time, seconds    9.55            8.31
>
> The numbers still seem wrong.  I'd expect to see almost exactly 2M minor
> faults with this test.
>
> Looky:
>
> #include <sys/mman.h>
> #include <stdio.h>
> #include <unistd.h>
> #include <stdlib.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
>
> #define G (1024 * 1024 * 1024)
>
> int main(int argc, char *argv[])
> {
>         char *p;
>         int fd;
>         unsigned long idx;
>         int sum = 0;
>
>         fd = open("foo", O_RDONLY);
>         if (fd < 0) {
>                 perror("open");
>                 exit(1);
>         }
>         p = mmap(NULL, 1 * G, PROT_READ, MAP_PRIVATE, fd, 0);
>         if (p == MAP_FAILED) {
>                 perror("mmap");
>                 exit(1);
>         }
>
>         for (idx = 0; idx < 1 * G; idx += 4096)
>                 sum += p[idx];
>         printf("%d\n", sum);
>         exit(0);
> }
>
> z:/home/akpm> /usr/bin/time ./a.out
> 0
> 0.05user 0.33system 0:00.38elapsed 99%CPU (0avgtext+0avgdata 4195856maxresident)k
> 0inputs+0outputs (0major+262264minor)pagefaults 0swaps
>
> z:/home/akpm> dc
> 16o
> 262264 4 * p
> 1001E0
>
> That's close!