lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Sat, 18 Apr 2020 13:27:53 +0000 From: David Laight <David.Laight@...LAB.COM> To: 'Mikulas Patocka' <mpatocka@...hat.com>, Dan Williams <dan.j.williams@...el.com> CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, "Peter Zijlstra" <peterz@...radead.org>, X86 ML <x86@...nel.org>, "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>, device-mapper development <dm-devel@...hat.com> Subject: RE: [PATCH] x86: introduce memcpy_flushcache_clflushopt 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)
Powered by blists - more mailing lists