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212ed884a1anon_pipe_write() takes pipe->mutex (aka "mutex protecting the whole thing") and then, from the per-iteration anon_pipe_get_page() helper, used to call alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT) once per page while still holding it. That allocation can sleep doing direct reclaim and/or runs memcg charging, which extends the critical section and stalls a concurrent reader on the very same mutex. Just pre-alloc the required pages before the lock in an array and just pop them inside the lock. This can improve the pipe throughput up to 48% and reduce the latency in 33%, easily seen when there is memory pressure and direct reclaim. Reviewed-by: Mateusz Guzik <mjguzik@gmail.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Link: https://patch.msgid.link/20260524-fix_pipe-v3-1-bb4a75d23a90@debian.org Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
1650 lines
40 KiB
1650 lines
40 KiB