From: Gabriel Krisman Bertazi <krisman@suse.de>
To: Ali Ahmet Memis <ali@iusegentoo.com>, Jens Axboe <axboe@kernel.dk>
Cc: Pavel Begunkov <asml.silence@gmail.com>,
io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: io_uring/memmap: compound allocation larger than accounted region
Date: Thu, 06 Aug 2026 12:21:54 -0400 [thread overview]
Message-ID: <87ik5ncj8d.fsf@mailhost.krisman.be> (raw)
In-Reply-To: <20260806154200.183725-1-ali@iusegentoo.com>
Ali Ahmet Memis <ali@iusegentoo.com> writes:
> io_mem_alloc_compound() allocates get_order(size) pages, while
> io_create_region() accounts reg->size >> PAGE_SHIFT. For a ring with 4096 SQ
> entries and the default CQ size that is 64 pages allocated against 37
> accounted.
>
> Is that intentional? memcg charges the full allocation, so only RLIMIT_MEMLOCK
> undercounts, and the gap is bounded by 2x. I did not want to send a patch for
> something that may well be a deliberate trade for the single folio.
I don't think that is intentional, beyond a simplification of the
code. If it is, it seems like a bad idea. Not necessarily harmful in
itself, but we should be accounting properly and not doing it if it goes
above the rlimit.
--
Gabriel Krisman Bertazi
prev parent reply other threads:[~2026-08-06 16:22 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-06 15:42 io_uring/memmap: compound allocation larger than accounted region Ali Ahmet Memis
2026-08-06 16:21 ` Gabriel Krisman Bertazi [this message]
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