From: David Laight <David.Laight@ACULAB.COM>
To: 'Mikulas Patocka' <mpatocka@redhat.com>,
Dan Williams <dan.j.williams@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Peter Zijlstra" <peterz@infradead.org>, X86 ML <x86@kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
device-mapper development <dm-devel@redhat.com>
Subject: RE: [PATCH] x86: introduce memcpy_flushcache_clflushopt
Date: Sat, 18 Apr 2020 13:27:53 +0000 [thread overview]
Message-ID: <69c2e011c5814255926f309dd50e6d67@AcuMS.aculab.com> (raw)
In-Reply-To: <alpine.LRH.2.02.2004170831530.16047@file01.intranet.prod.int.rdu2.redhat.com>
From: Mikulas Patocka
> Sent: 17 April 2020 13:47
...
> Index: linux-2.6/drivers/md/dm-writecache.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/dm-writecache.c 2020-04-17 14:06:35.139999000 +0200
> +++ linux-2.6/drivers/md/dm-writecache.c 2020-04-17 14:06:35.129999000 +0200
> @@ -1166,7 +1166,10 @@ static void bio_copy_block(struct dm_wri
> }
> } else {
> flush_dcache_page(bio_page(bio));
> - memcpy_flushcache(data, buf, size);
> + if (likely(size > 512))
> + memcpy_flushcache_clflushopt(data, buf, size);
> + else
> + memcpy_flushcache(data, buf, size);
Hmmm... have you looked at how long clflush actually takes?
It isn't too bad if you just do a small number, but using it
to flush large buffers can be very slow.
I've an Ivy bridge system where the X-server process requests the
frame buffer be flushed out every 10 seconds (no idea why).
With my 2560x1440 monitor this takes over 3ms.
This really needs a cond_resched() every few clflush instructions.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-04-18 13:28 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-07 15:01 [PATCH] memcpy_flushcache: use cache flusing for larger lengths Mikulas Patocka
2020-04-07 16:09 ` Andy Lutomirski
2020-04-07 16:33 ` Mikulas Patocka
2020-04-07 17:52 ` Dan Williams
2020-04-08 18:54 ` Mikulas Patocka
2020-04-08 19:29 ` Dan Williams
2020-04-09 14:36 ` Mikulas Patocka
2020-04-16 8:24 ` Mikulas Patocka
2020-04-16 18:28 ` Dan Williams
2020-04-17 12:47 ` [PATCH] x86: introduce memcpy_flushcache_clflushopt Mikulas Patocka
2020-04-17 17:57 ` Dan Williams
2020-04-17 20:45 ` Thomas Gleixner
2020-04-20 13:47 ` [PATCH v2] x86: introduce memcpy_flushcache_single Mikulas Patocka
2020-04-21 18:43 ` Dan Williams
2020-04-18 13:27 ` David Laight [this message]
2020-04-18 15:21 ` [PATCH] x86: introduce memcpy_flushcache_clflushopt Mikulas Patocka
2020-04-19 17:48 ` David Laight
2020-04-20 4:49 ` Dan Williams
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