Willy Tarreau 758cb450a2 OPTIM: sink: drop the sink lock used to count drops ... The sink lock was made to prevent event producers from passing while there were other threads trying to print a "dropped" message, in order to guarantee the absence of reordering. It has a serious impact however, which is that all threads need to take the read lock when producing a regular trace even when there's no reader. This patch takes a different approach. The drop counter is shifted left by one so that the lowest bit is used to indicate that one thread is already taking care of trying to dump the counter. Threads only read this value normally, and will only try to change it if it's non-null, in which case they'll first check if they are the first ones trying to dump it, otherwise will simply count another drop and leave. This has a large benefit. First, it will avoid the locking that causes stalls as soon as a slow reader is present. Second, it avoids any write on the fast path as long as there's no drop. And it remains very lightweight since we just need to add +2 or subtract 2*dropped in operations, while offering the guarantee that the sink_write() has succeeded before unlocking the counter. While a reader was previously limiting the traffic to 11k RPS under 4C/8T, now we reach 36k RPS vs 14k with no reader, so readers will no longer slow the traffic down and will instead even speed it up due to avoiding the contention down the chain in the ring. The locking cost dropped from ~75% to ~60% now (it's in ring_write now).		2024-03-09 11:23:52 +01:00
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haproxy	OPTIM: sink: drop the sink lock used to count drops	2024-03-09 11:23:52 +01:00
import	BUILD: tree-wide: fix a few missing includes in a few files	2024-03-05 11:50:34 +01:00
make	BUILD: makefile: also define cmd_CXX to pretty-print C++ build commands	2024-01-26 18:54:23 +01:00