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From: Ali Ahmet Memis <ali@iusegentoo.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Pavel Begunkov <asml.silence@gmail.com>,
	io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: io_uring/memmap: compound allocation larger than accounted region
Date: Thu,  6 Aug 2026 15:42:00 +0000	[thread overview]
Message-ID: <20260806154200.183725-1-ali@iusegentoo.com> (raw)

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.

Thanks,
Ali

             reply	other threads:[~2026-08-06 15:42 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-06 15:42 Ali Ahmet Memis [this message]
2026-08-06 16:21 ` io_uring/memmap: compound allocation larger than accounted region Gabriel Krisman Bertazi

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