[#LU-16741] defer & parallelize parts of ptlrpc_free

[LU-16741] defer & parallelize parts of ptlrpc_free_committed Created: 15/Apr/23 Updated: 11/Jan/24
Status:	Open
Project:	Lustre
Component/s:	None
Affects Version/s:	None
Fix Version/s:	None

Type:

Improvement

Priority:

Minor

Reporter:

Patrick Farrell

Assignee:

Patrick Farrell

Resolution:

Unresolved

Votes:

Labels:

None

Rank (Obsolete):

9223372036854775807

Description

ptlrpc_free_committed can be extremely time consuming if there are many async requests outstanding, such as with small async DIO as potentially created by LU-13805, or in other unusual circumstances.

The biggest problem is that we do all the work in a single threaded manner while holding the imp_lock. A recent patch ( https://review.whamcloud.com/c/fs/lustre-release/+/48629 ) changed it so the thread will release the lock and 'hand off' to a waiter if it's running too long (and there is a waiter), but the process is still serial, so this avoids stalls, but there's no improvement in overall efficiency.

Most of the work (in terms of time consumed) in ptlrpc_free_committed can be deferred and moved out from under the imp_lock. If we do this, we can also use our ability to know there is a waiter to 'batch' sets of requests, where we find a certain number, then hand off to the waiter. This has the effect of parallelizing this work and should speed it up significantly.

Comments

Comment by Gerrit Updater [ 15/Apr/23 ]

"Patrick Farrell <pfarrell@whamcloud.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50645
Subject: LU-16741 ptlrpc: defer & parallelize free_committed
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 0428f2ccc7653c4d07183719c2b13826a8154bed

Comment by Gerrit Updater [ 18/Apr/23 ]

"Patrick Farrell <pfarrell@whamcloud.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50677
Subject: LU-16741 ptlrpc: rename ptlrpc_req_finished
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 5d918d81eeddb1b8f6513bed6703bf5ab50d4f71

Comment by Gerrit Updater [ 18/Apr/23 ]

"Patrick Farrell <pfarrell@whamcloud.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50678
Subject: LU-16741 ptlrpc: refactor __ptlrpc_req_put
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: f4458ce35e8762ab6c0361bb1af57564a108dec4

Comment by Gerrit Updater [ 18/Apr/23 ]

"Patrick Farrell <pfarrell@whamcloud.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50679
Subject: LU-16741 ptlrpc: rename __ functions
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: f632118835661d46f5cc399f4e4dbbe0d48edc33

Comment by Gerrit Updater [ 18/Apr/23 ]

"Patrick Farrell <pfarrell@whamcloud.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50680
Subject: LU-16741 ptlrpc: rename ptlrpc_free_request
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: faf9bb4fb7006e71f13702fe2a6987d6de29b374

Comment by Gerrit Updater [ 18/Apr/23 ]

"Patrick Farrell <pfarrell@whamcloud.com>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50681
Subject: LU-16741 ptlrpc: remove unnecessary asserts
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 5e721beefb0178f68bc6e79fb2e965e657563c8a