From: Mikulas Patocka <mpatocka@redhat.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: device-mapper development <dm-devel@redhat.com>,
Mike Snitzer <snitzer@redhat.com>,
linux-nvdimm <linux-nvdimm@lists.01.org>
Subject: Re: [patch 4/4] dm-writecache: use new API for flushing
Date: Thu, 31 May 2018 11:31:08 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1805311127001.31059@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <CAPcyv4gzFbdBbUhPJ6W4mTJWAkvqVw_4FVhVdePEJzc28Sg-Sg@mail.gmail.com>
On Thu, 31 May 2018, Dan Williams wrote:
> On Thu, May 31, 2018 at 1:19 AM, Mikulas Patocka <mpatocka@redhat.com> wrote:
> >
> >
> > On Wed, 30 May 2018, Dan Williams wrote:
> >
> >> > Great find! Thanks for the due diligence. Feel free to add:
> >> >
> >> > Acked-by: Dan Williams <dan.j.williams@intel.com>
> >> >
> >> > ...on the reworks to unify ARM and x86.
> >>
> >> One more note. The side effect of not using dax_flush() is that you
> >> may end up flushing caches on systems where the platform has asserted
> >> it will take responsibility for flushing caches at power loss. If /
> >> when those systems become more prevalent we may want to think of a way
> >> to combine the non-temporal optimization and the cache-flush-bypass
> >> optimizations. However that is something that can wait for a later
> >> change beyond 4.18.
> >
> > We could define memcpy_flushpmem, that falls back to memcpy or
> > memcpy_flushcache, depending on whether the platform flushes the caches at
> > power loss or not.
>
> The problem is that some platforms only power fail protect a subset of
> the physical address range,
How can this be? A psysical address may be cached on any CPU, so either
there is enough power to flush all the CPUs' caches or there isn't.
How does the CPU design that protects only a part of physical addresses
look like?
> but yes, if the platform makes a global
> assertion we can globally replace memcpy_flushpmem() with plain
> memcpy.
Mikulas
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WARNING: multiple messages have this Message-ID (diff)
From: Mikulas Patocka <mpatocka-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: 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: [patch 4/4] dm-writecache: use new API for flushing
Date: Thu, 31 May 2018 11:31:08 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1805311127001.31059@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <CAPcyv4gzFbdBbUhPJ6W4mTJWAkvqVw_4FVhVdePEJzc28Sg-Sg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Thu, 31 May 2018, Dan Williams wrote:
> On Thu, May 31, 2018 at 1:19 AM, Mikulas Patocka <mpatocka-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> >
> >
> > On Wed, 30 May 2018, Dan Williams wrote:
> >
> >> > Great find! Thanks for the due diligence. Feel free to add:
> >> >
> >> > Acked-by: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> >> >
> >> > ...on the reworks to unify ARM and x86.
> >>
> >> One more note. The side effect of not using dax_flush() is that you
> >> may end up flushing caches on systems where the platform has asserted
> >> it will take responsibility for flushing caches at power loss. If /
> >> when those systems become more prevalent we may want to think of a way
> >> to combine the non-temporal optimization and the cache-flush-bypass
> >> optimizations. However that is something that can wait for a later
> >> change beyond 4.18.
> >
> > We could define memcpy_flushpmem, that falls back to memcpy or
> > memcpy_flushcache, depending on whether the platform flushes the caches at
> > power loss or not.
>
> The problem is that some platforms only power fail protect a subset of
> the physical address range,
How can this be? A psysical address may be cached on any CPU, so either
there is enough power to flush all the CPUs' caches or there isn't.
How does the CPU design that protects only a part of physical addresses
look like?
> but yes, if the platform makes a global
> assertion we can globally replace memcpy_flushpmem() with plain
> memcpy.
Mikulas
next prev parent reply other threads:[~2018-05-31 15:31 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
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 [this message]
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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