linux-kernel - [PATCH v3] IB/mlx5: Reduce max order of memory allocated for xlt update

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Message-Id: <1617425635-35631-1-git-send-email-praveen.kannoju@oracle.com>
Date:   Sat,  3 Apr 2021 04:53:55 +0000
From:   Praveen Kumar Kannoju <praveen.kannoju@...cle.com>
To:     leon@...nel.org, dledford@...hat.com, jgg@...pe.ca,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     rajesh.sivaramasubramaniom@...cle.com,
        rama.nichanamatlu@...cle.com, aruna.ramakrishna@...cle.com,
        jeffery.yoder@...cle.com,
        Praveen Kumar Kannoju <praveen.kannoju@...cle.com>
Subject: [PATCH v3] IB/mlx5: Reduce max order of memory allocated for xlt update

To update xlt (during mlx5_ib_reg_user_mr()), the driver can request up to
1 MB (order-8) memory, depending on the size of the MR. This costly
allocation can sometimes take very long to return (a few seconds). This
causes the calling application to hang for a long time, especially when the
system is fragmented.  To avoid these long latency spikes, the calls the
higher order allocations need to fail faster in case they are not
available. In order to acheive this we need __GFP_NORETRY flag in the
gfp_mask before during fetching the free pages. This patch adds this flag
to the mask.

Signed-off-by: Praveen Kumar Kannoju <praveen.kannoju@...cle.com>
---
 drivers/infiniband/hw/mlx5/mr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index db05b0e..429e7aa6 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -1028,7 +1028,7 @@ static void *mlx5_ib_alloc_xlt(size_t *nents, size_t ent_size, gfp_t gfp_mask)
 	 */
 	might_sleep();

-	gfp_mask |= __GFP_ZERO;
+	gfp_mask |= __GFP_ZERO | __GFP_NORETRY;

 	/*
 	 * If the system already has a suitable high order page then just use
-- 
1.8.3.1