From: Mikulas Patocka <mpatocka@redhat.com>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>,
device-mapper development <dm-devel@redhat.com>,
Mike Snitzer <snitzer@redhat.com>,
linux-nvdimm <linux-nvdimm@lists.01.org>
Subject: Re: [dm-devel] [patch 4/4] dm-writecache: use new API for flushing
Date: Wed, 30 May 2018 09:51:16 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1805300949220.16696@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <x49h8mpmf8v.fsf@segfault.boston.devel.redhat.com>
On Wed, 30 May 2018, Jeff Moyer wrote:
> Dan Williams <dan.j.williams@intel.com> writes:
>
> > When I read your patch I came away with the impression that ARM had
> > not added memcpy_flushcache() yet and you were working around that
> > fact. Now that I look, ARM *does* define memcpy_flushcache() and
> > you're avoiding it. You use memcpy+arch_wb_pmem where arch_wb_pmem on
> > ARM64 is defined as __clean_dcache_area_pop(dst, cnt). The ARM
> > memcpy_flushcache() implementation is:
> >
> > memcpy(dst, src, cnt);
> > __clean_dcache_area_pop(dst, cnt);
> >
> > So, I do not see how what you're doing is any less work unless you are
> > flushing less than you copy?
> >
> > If memcpy_flushcache() is slower than memcpy + arch_wb_pmem then the
> > ARM implementation is broken and that needs to be addressed not worked
> > around in a driver.
>
> I think Mikulas wanted to batch up multiple copies and flush at the
> end. According to his commit message, that batching gained him 2%
> performance.
>
> -Jeff
No - this 2% difference is inlined memcpy_flushcache() vs out-of-line
memcpy_flushcache().
I thought that dax_flush() performed 12% better memcpy_flushcache() - but
the reason why it performed better was - that it was not flushing the
cache at all.
Mikulas
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WARNING: multiple messages have this Message-ID (diff)
From: Mikulas Patocka <mpatocka-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
device-mapper development
<dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Mike Snitzer <snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
linux-nvdimm
<linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>
Subject: Re: [dm-devel] [patch 4/4] dm-writecache: use new API for flushing
Date: Wed, 30 May 2018 09:51:16 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1805300949220.16696@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <x49h8mpmf8v.fsf-RRHT56Q3PSP4kTEheFKJxxDDeQx5vsVwAInAS/Ez/D0@public.gmane.org>
On Wed, 30 May 2018, Jeff Moyer wrote:
> Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> writes:
>
> > When I read your patch I came away with the impression that ARM had
> > not added memcpy_flushcache() yet and you were working around that
> > fact. Now that I look, ARM *does* define memcpy_flushcache() and
> > you're avoiding it. You use memcpy+arch_wb_pmem where arch_wb_pmem on
> > ARM64 is defined as __clean_dcache_area_pop(dst, cnt). The ARM
> > memcpy_flushcache() implementation is:
> >
> > memcpy(dst, src, cnt);
> > __clean_dcache_area_pop(dst, cnt);
> >
> > So, I do not see how what you're doing is any less work unless you are
> > flushing less than you copy?
> >
> > If memcpy_flushcache() is slower than memcpy + arch_wb_pmem then the
> > ARM implementation is broken and that needs to be addressed not worked
> > around in a driver.
>
> I think Mikulas wanted to batch up multiple copies and flush at the
> end. According to his commit message, that batching gained him 2%
> performance.
>
> -Jeff
No - this 2% difference is inlined memcpy_flushcache() vs out-of-line
memcpy_flushcache().
I thought that dax_flush() performed 12% better memcpy_flushcache() - but
the reason why it performed better was - that it was not flushing the
cache at all.
Mikulas
next prev parent reply other threads:[~2018-05-30 13:51 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-19 5:25 [patch 0/4] dm-writecache patches Mikulas Patocka
2018-05-19 5:25 ` [patch 1/4] x86: optimize memcpy_flushcache Mikulas Patocka
2018-05-19 14:21 ` Dan Williams
2018-05-24 18:20 ` [PATCH v2] " Mike Snitzer
2018-06-18 13:23 ` [PATCH v2 RESEND] " Mike Snitzer
2018-06-18 13:23 ` Mike Snitzer
2018-06-21 14:31 ` Ingo Molnar
2018-06-22 1:19 ` Mikulas Patocka
2018-06-22 1:19 ` Mikulas Patocka
2018-06-22 1:30 ` Ingo Molnar
2018-08-08 21:22 ` [PATCH v3 " Mikulas Patocka
2018-09-10 13:18 ` Ingo Molnar
2018-09-11 6:22 ` [tip:x86/asm] x86/asm: Optimize memcpy_flushcache() tip-bot for Mikulas Patocka
2018-05-19 5:25 ` [patch 2/4] swait: export the symbols __prepare_to_swait and __finish_swait Mikulas Patocka
2018-05-22 6:34 ` Christoph Hellwig
2018-05-22 18:52 ` Mike Snitzer
2018-05-23 9:21 ` Peter Zijlstra
2018-05-23 15:10 ` Mike Snitzer
2018-05-23 18:10 ` [PATCH v2] swait: export " Mike Snitzer
2018-05-23 20:38 ` Mikulas Patocka
2018-05-23 21:51 ` Mike Snitzer
2018-05-24 14:10 ` Peter Zijlstra
2018-05-24 15:09 ` Mike Snitzer
2018-05-19 5:25 ` [patch 3/4] dm-writecache Mikulas Patocka
2018-05-22 6:37 ` Christoph Hellwig
2018-05-19 5:25 ` [patch 4/4] dm-writecache: use new API for flushing Mikulas Patocka
2018-05-22 6:39 ` [dm-devel] " Christoph Hellwig
2018-05-22 6:39 ` Christoph Hellwig
2018-05-22 18:41 ` Mike Snitzer
2018-05-22 18:41 ` Mike Snitzer
2018-05-22 19:00 ` Dan Williams
2018-05-22 19:00 ` Dan Williams
2018-05-22 19:19 ` Mike Snitzer
2018-05-22 19:19 ` Mike Snitzer
2018-05-22 19:27 ` Dan Williams
2018-05-22 19:27 ` Dan Williams
2018-05-22 20:52 ` Mike Snitzer
2018-05-22 20:52 ` Mike Snitzer
2018-05-22 22:53 ` [dm-devel] " Jeff Moyer
2018-05-22 22:53 ` Jeff Moyer
2018-05-23 20:57 ` Mikulas Patocka
2018-05-23 20:57 ` Mikulas Patocka
2018-05-28 13:52 ` Mikulas Patocka
2018-05-28 13:52 ` Mikulas Patocka
2018-05-28 17:41 ` Dan Williams
2018-05-28 17:41 ` Dan Williams
2018-05-30 13:42 ` [dm-devel] " Jeff Moyer
2018-05-30 13:42 ` Jeff Moyer
2018-05-30 13:51 ` Mikulas Patocka [this message]
2018-05-30 13:51 ` Mikulas Patocka
2018-05-30 13:52 ` Jeff Moyer
2018-05-30 13:52 ` Jeff Moyer
2018-05-24 8:15 ` Mikulas Patocka
2018-05-24 8:15 ` Mikulas Patocka
2018-05-25 3:12 ` Dan Williams
2018-05-25 6:17 ` Mikulas Patocka
2018-05-25 12:51 ` Mike Snitzer
2018-05-25 12:51 ` Mike Snitzer
2018-05-25 15:57 ` Dan Williams
2018-05-25 15:57 ` Dan Williams
2018-05-26 7:02 ` Mikulas Patocka
2018-05-26 7:02 ` Mikulas Patocka
2018-05-26 15:26 ` Dan Williams
2018-05-26 15:26 ` Dan Williams
2018-05-28 13:32 ` Mikulas Patocka
2018-05-28 13:32 ` Mikulas Patocka
2018-05-28 18:14 ` Dan Williams
2018-05-28 18:14 ` Dan Williams
2018-05-30 13:07 ` Mikulas Patocka
2018-05-30 13:07 ` Mikulas Patocka
2018-05-30 13:16 ` Mike Snitzer
2018-05-30 13:16 ` Mike Snitzer
2018-05-30 13:21 ` Mikulas Patocka
2018-05-30 13:21 ` Mikulas Patocka
2018-05-30 13:26 ` Mike Snitzer
2018-05-30 13:26 ` Mike Snitzer
2018-05-30 13:33 ` Mikulas Patocka
2018-05-30 13:33 ` Mikulas Patocka
2018-05-30 13:54 ` Mike Snitzer
2018-05-30 13:54 ` Mike Snitzer
2018-05-30 14:09 ` Mikulas Patocka
2018-05-30 14:09 ` Mikulas Patocka
2018-05-30 14:21 ` Mike Snitzer
2018-05-30 14:21 ` Mike Snitzer
2018-05-30 14:46 ` Mikulas Patocka
2018-05-30 14:46 ` Mikulas Patocka
2018-05-31 3:42 ` Mike Snitzer
2018-05-31 3:42 ` Mike Snitzer
2018-06-03 15:03 ` Mikulas Patocka
2018-06-03 15:03 ` Mikulas Patocka
2018-05-31 3:39 ` Mike Snitzer
2018-05-31 3:39 ` Mike Snitzer
2018-05-31 8:16 ` Mikulas Patocka
2018-05-31 8:16 ` Mikulas Patocka
2018-05-31 12:09 ` Mike Snitzer
2018-05-31 12:09 ` Mike Snitzer
2018-05-30 15:58 ` Dan Williams
2018-05-30 15:58 ` Dan Williams
2018-05-30 22:39 ` Dan Williams
2018-05-30 22:39 ` Dan Williams
2018-05-31 8:19 ` Mikulas Patocka
2018-05-31 8:19 ` Mikulas Patocka
2018-05-31 14:51 ` Dan Williams
2018-05-31 14:51 ` Dan Williams
2018-05-31 15:31 ` Mikulas Patocka
2018-05-31 15:31 ` Mikulas Patocka
2018-05-31 16:39 ` Dan Williams
2018-05-31 16:39 ` Dan Williams
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