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tcp_splice: A typo three years ago and SO_RCVLOWAT is gone

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In commit e5eefe7743 ("tcp: Refactor to use events instead of
states, split out spliced implementation"), this:

			if (!bitmap_isset(rcvlowat_set, conn - ts) &&
			    readlen > (long)c->tcp.pipe_size / 10) {

(note the !) became:

			if (conn->flags & lowat_set_flag &&
			    readlen > (long)c->tcp.pipe_size / 10) {

in the new tcp_splice_sock_handler().

We want to check, there, if we should set SO_RCVLOWAT, only if we
haven't set it already.

But, instead, we're checking if it's already set before we set it, so
we'll never set it, of course.

Fix the check and re-enable the functionality, which should give us
improved CPU utilisation in non-interactive cases where we are not
transferring at full pipe capacity.

Fixes: e5eefe7743 ("tcp: Refactor to use events instead of states, split out spliced implementation")
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
Stefano Brivio 2025-02-16 08:31:13 +01:00
parent 667caa09c6
commit 01b6a164d9
1 changed files with 1 additions and 1 deletions

2
tcp_splice.c
View file

@ -556,7 +556,7 @@ eintr:
if (readlen >= (long)c->tcp.pipe_size * 10 / 100)
continue;
if (conn->flags & lowat_set_flag &&
if (!(conn->flags & lowat_set_flag) &&
readlen > (long)c->tcp.pipe_size / 10) {
int lowat = c->tcp.pipe_size / 4;