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From: Pavel Begunkov <[email protected]>
To: [email protected]
Cc: Jens Axboe <[email protected]>, [email protected]
Subject: [PATCH for-next v2 18/25] io_uring: limit number hash buckets
Date: Tue, 14 Jun 2022 15:37:08 +0100	[thread overview]
Message-ID: <57a30f28ac6235d7913444ff3bee9bc5ce70f5d4.1655213915.git.asml.silence@gmail.com> (raw)
In-Reply-To: <[email protected]>

Don't allocate to many hash/cancellation buckets, there might be too
many, clamp it to 8 bits, or 256 * 64B = 16KB. We don't usually have too
many requests, and 256 buckets should be enough, especially since we
do hash search only in the cancellation path.

Signed-off-by: Pavel Begunkov <[email protected]>
---
 io_uring/io_uring.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 4d94757e6e28..2a7a5db12a0e 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -710,12 +710,12 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 
 	/*
 	 * Use 5 bits less than the max cq entries, that should give us around
-	 * 32 entries per hash list if totally full and uniformly spread.
+	 * 32 entries per hash list if totally full and uniformly spread, but
+	 * don't keep too many buckets to not overconsume memory.
 	 */
-	hash_bits = ilog2(p->cq_entries);
-	hash_bits -= 5;
-	if (hash_bits <= 0)
-		hash_bits = 1;
+	hash_bits = ilog2(p->cq_entries) - 5;
+	hash_bits = clamp(hash_bits, 1, 8);
+
 	ctx->cancel_hash_bits = hash_bits;
 	ctx->cancel_hash =
 		kmalloc((1U << hash_bits) * sizeof(struct io_hash_bucket),
-- 
2.36.1



  parent reply	other threads:[~2022-06-14 14:38 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-14 14:36 [PATCH for-next v2 00/25] 5.20 cleanups and poll optimisations Pavel Begunkov
2022-06-14 14:36 ` [PATCH for-next v2 01/25] io_uring: make reg buf init consistent Pavel Begunkov
2022-06-14 14:36 ` [PATCH for-next v2 02/25] io_uring: move defer_list to slow data Pavel Begunkov
2022-06-14 14:36 ` [PATCH for-next v2 03/25] io_uring: better caching for ctx timeout fields Pavel Begunkov
2022-06-14 14:36 ` [PATCH for-next v2 04/25] io_uring: refactor ctx slow data placement Pavel Begunkov
2022-06-14 14:36 ` [PATCH for-next v2 05/25] io_uring: move small helpers to headers Pavel Begunkov
2022-06-14 14:36 ` [PATCH for-next v2 06/25] io_uring: explain io_wq_work::cancel_seq placement Pavel Begunkov
2022-06-14 14:36 ` [PATCH for-next v2 07/25] io_uring: inline ->registered_rings Pavel Begunkov
2022-06-14 14:36 ` [PATCH for-next v2 08/25] io_uring: don't set REQ_F_COMPLETE_INLINE in tw Pavel Begunkov
2022-06-14 14:36 ` [PATCH for-next v2 09/25] io_uring: never defer-complete multi-apoll Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 10/25] io_uring: kill REQ_F_COMPLETE_INLINE Pavel Begunkov
2022-06-15  8:20   ` Hao Xu
2022-06-14 14:37 ` [PATCH for-next v2 11/25] io_uring: refactor io_req_task_complete() Pavel Begunkov
2022-06-14 17:45   ` Hao Xu
2022-06-14 17:52     ` Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 12/25] io_uring: don't inline io_put_kbuf Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 13/25] io_uring: remove check_cq checking from hot paths Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 14/25] io_uring: poll: remove unnecessary req->ref set Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 15/25] io_uring: switch cancel_hash to use per entry spinlock Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 16/25] io_uring: pass poll_find lock back Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 17/25] io_uring: clean up io_try_cancel Pavel Begunkov
2022-06-14 14:37 ` Pavel Begunkov [this message]
2022-06-14 14:37 ` [PATCH for-next v2 19/25] io_uring: clean up io_ring_ctx_alloc Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 20/25] io_uring: use state completion infra for poll reqs Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 21/25] io_uring: add IORING_SETUP_SINGLE_ISSUER Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 22/25] io_uring: pass hash table into poll_find Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 23/25] io_uring: introduce a struct for hash table Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 24/25] io_uring: propagate locking state to poll cancel Pavel Begunkov
2022-06-14 14:37 ` [PATCH for-next v2 25/25] io_uring: mutex locked poll hashing Pavel Begunkov

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