linux-kernel - Re: [RFC PATCH 5/6] zsmalloc: introduce handle mapping API

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <emzwud4amof3lrcbnnmsjhwiuoacxuwvzj7pnt5gdybirm5bk5@npchq2yxvr5t>
Date: Tue, 28 Jan 2025 18:38:35 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Minchan Kim <minchan@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Nhat Pham <nphamcs@...il.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [RFC PATCH 5/6] zsmalloc: introduce handle mapping API

On (25/01/28 14:29), Sergey Senozhatsky wrote:
> Maybe copy-in is just an okay thing to do.  Let me try to measure.

Naaah, not really okay.  On our memory-pressure test (4GB device, 4
CPUs) that kmap_local thingy appears to save approx 6GB of memcpy().

CPY stats: 734954 1102903168 4926116 6566654656

There were 734954 cases when we memcpy() [object spans two pages] with
accumulated size of 1102903168 bytes, and 4926116 cases when we took
a shortcut via kmap_local and avoided memcpy(), with accumulated size
of 6566654656 bytes.

In both cases I counted only RO direction for map, and WO direction
for unmap.