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From: Pavel Begunkov <[email protected]>
To: [email protected]
Cc: Jens Axboe <[email protected]>, [email protected]
Subject: [PATCH for-next v3 09/16] io_uring: limit the number of cancellation buckets
Date: Thu, 16 Jun 2022 10:22:05 +0100	[thread overview]
Message-ID: <b9620c8072ba61a2d50eba894b89bd93a94a9abd.1655371007.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 d0242e5c8d0a..97113c71e881 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -254,12 +254,12 @@ 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:[~2022-06-16  9:22 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-16  9:21 [PATCH for-next v3 00/16] 5.20 cleanups and poll optimisations Pavel Begunkov
2022-06-16  9:21 ` [PATCH for-next v3 01/16] io_uring: rw: delegate sync completions to core io_uring Pavel Begunkov
2022-06-16  9:21 ` [PATCH for-next v3 02/16] io_uring: kill REQ_F_COMPLETE_INLINE Pavel Begunkov
2022-06-16  9:21 ` [PATCH for-next v3 03/16] io_uring: refactor io_req_task_complete() Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 04/16] io_uring: don't inline io_put_kbuf Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 05/16] io_uring: poll: remove unnecessary req->ref set Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 06/16] io_uring: switch cancel_hash to use per entry spinlock Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 07/16] io_uring: pass poll_find lock back Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 08/16] io_uring: clean up io_try_cancel Pavel Begunkov
2022-06-16  9:22 ` Pavel Begunkov [this message]
2022-06-16  9:22 ` [PATCH for-next v3 10/16] io_uring: clean up io_ring_ctx_alloc Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 11/16] io_uring: use state completion infra for poll reqs Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 12/16] io_uring: add IORING_SETUP_SINGLE_ISSUER Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 13/16] io_uring: pass hash table into poll_find Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 14/16] io_uring: introduce a struct for hash table Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 15/16] io_uring: propagate locking state to poll cancel Pavel Begunkov
2022-06-16  9:22 ` [PATCH for-next v3 16/16] io_uring: mutex locked poll hashing Pavel Begunkov
2022-06-17 15:35   ` Nathan Chancellor
2022-06-18 12:07     ` Pavel Begunkov
2022-06-16 13:18 ` [PATCH for-next v3 00/16] 5.20 cleanups and poll optimisations Jens Axboe
2022-06-16 15:58 ` Hao Xu

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