PS-11120 [trunk]: Reduce contention on BUF_BLOCK_MUTEX by reading ahead the access_time#6044
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PS-11120 [trunk]: Reduce contention on BUF_BLOCK_MUTEX by reading ahead the access_time#6044polchawa-percona wants to merge 1 commit into
polchawa-percona wants to merge 1 commit into
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…ad the access_time https://perconadev.atlassian.net/browse/PS-11120 This patch reduces contention inside buf_page_optimistic_get. We acquire the BUF_BLOCK_MUTEX twice there. The second time we acquire it only to update the access time, and only if it was zero. By reading the access time the first time we hold the mutex, we can skip re-acquiring it when the page has already been accessed (non-zero access time), which is the common case for hot pages. This is safe because: the second time the mutex is taken the access time is re-checked anyway; access time is never reset to zero (except when a page is reinitialized); and the page cannot be reinitialized meanwhile because it was buffer-fixed on first access. This is a contribution from Anna Glasgall <aglasgal@akamai.com> / Akamai, with a minor fix added.
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https://perconadev.atlassian.net/browse/PS-11120
trunk equivalent of #6031.
This patch reduces contention inside
buf_page_optimistic_get. We acquire the BUF_BLOCK_MUTEX twice there, but the second time only to update the access time — and only if it was zero. By reading the access time the first time we hold the mutex, we can avoid re-acquiring it when the page has already been accessed (non-zero access time), which is the common case for hot pages.Why it is safe:
buf_block_buf_fix_inc) on first access and stays alive until unfixed.This is a contribution from Anna Glasgall aglasgal@akamai.com / Akamai, with a minor fix added.