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author | Yossi Gottlieb <yossigo@gmail.com> | 2021-03-22 13:25:58 +0200 |
---|---|---|
committer | GitHub <noreply@github.com> | 2021-03-22 13:25:58 +0200 |
commit | c3df27d1ea3eeff8ad4d0bec2bfc2646efb9843f (patch) | |
tree | 511ce3909a2b689e8bdaa1ad0563cec411893481 /src/childinfo.c | |
parent | 2f717c156a0bca757b8a8dfacf27e9cbeb60f99d (diff) | |
download | redis-c3df27d1ea3eeff8ad4d0bec2bfc2646efb9843f.tar.gz |
Fix slowdown due to child reporting CoW. (#8645)
Reading CoW from /proc/<pid>/smaps can be slow with large processes on
some platforms.
This measures the time it takes to read CoW info and limits the duty
cycle of future updates to roughly 1/100.
As current_cow_size no longer represnets a current, fixed interval value
there is also a new current_cow_size_age field that provides information
about the age of the size value, in seconds.
Diffstat (limited to 'src/childinfo.c')
-rw-r--r-- | src/childinfo.c | 49 |
1 files changed, 37 insertions, 12 deletions
diff --git a/src/childinfo.c b/src/childinfo.c index e3f33a96c..4f0a42001 100644 --- a/src/childinfo.c +++ b/src/childinfo.c @@ -33,6 +33,7 @@ typedef struct { size_t keys; size_t cow; + monotime cow_updated; double progress; childInfoType information_type; /* Type of information */ } child_info_data; @@ -69,18 +70,39 @@ void closeChildInfoPipe(void) { void sendChildInfoGeneric(childInfoType info_type, size_t keys, double progress, char *pname) { if (server.child_info_pipe[1] == -1) return; - child_info_data data = {0}; /* zero everything, including padding to sattisfy valgrind */ + static monotime cow_updated = 0; + static uint64_t cow_update_cost = 0; + static size_t cow = 0; + + child_info_data data = {0}; /* zero everything, including padding to satisfy valgrind */ + + /* When called to report current info, we need to throttle down CoW updates as they + * can be very expensive. To do that, we measure the time it takes to get a reading + * and schedule the next reading to happen not before time*CHILD_COW_COST_FACTOR + * passes. */ + + monotime now = getMonotonicUs(); + if (info_type != CHILD_INFO_TYPE_CURRENT_INFO || + !cow_updated || + now - cow_updated > cow_update_cost * CHILD_COW_DUTY_CYCLE) + { + cow = zmalloc_get_private_dirty(-1); + cow_updated = getMonotonicUs(); + cow_update_cost = cow_updated - now; + + if (cow) { + serverLog((info_type == CHILD_INFO_TYPE_CURRENT_INFO) ? LL_VERBOSE : LL_NOTICE, + "%s: %zu MB of memory used by copy-on-write", + pname, data.cow / (1024 * 1024)); + } + } + data.information_type = info_type; data.keys = keys; - data.cow = zmalloc_get_private_dirty(-1); + data.cow = cow; + data.cow_updated = cow_updated; data.progress = progress; - if (data.cow) { - serverLog((info_type == CHILD_INFO_TYPE_CURRENT_INFO) ? LL_VERBOSE : LL_NOTICE, - "%s: %zu MB of memory used by copy-on-write", - pname, data.cow/(1024*1024)); - } - ssize_t wlen = sizeof(data); if (write(server.child_info_pipe[1], &data, wlen) != wlen) { @@ -89,9 +111,10 @@ void sendChildInfoGeneric(childInfoType info_type, size_t keys, double progress, } /* Update Child info. */ -void updateChildInfo(childInfoType information_type, size_t cow, size_t keys, double progress) { +void updateChildInfo(childInfoType information_type, size_t cow, monotime cow_updated, size_t keys, double progress) { if (information_type == CHILD_INFO_TYPE_CURRENT_INFO) { server.stat_current_cow_bytes = cow; + server.stat_current_cow_updated = cow_updated; server.stat_current_save_keys_processed = keys; if (progress != -1) server.stat_module_progress = progress; } else if (information_type == CHILD_INFO_TYPE_AOF_COW_SIZE) { @@ -107,7 +130,7 @@ void updateChildInfo(childInfoType information_type, size_t cow, size_t keys, do * if complete data read into the buffer, * data is stored into *buffer, and returns 1. * otherwise, the partial data is left in the buffer, waiting for the next read, and returns 0. */ -int readChildInfo(childInfoType *information_type, size_t *cow, size_t *keys, double* progress) { +int readChildInfo(childInfoType *information_type, size_t *cow, monotime *cow_updated, size_t *keys, double* progress) { /* We are using here a static buffer in combination with the server.child_info_nread to handle short reads */ static child_info_data buffer; ssize_t wlen = sizeof(buffer); @@ -124,6 +147,7 @@ int readChildInfo(childInfoType *information_type, size_t *cow, size_t *keys, do if (server.child_info_nread == wlen) { *information_type = buffer.information_type; *cow = buffer.cow; + *cow_updated = buffer.cow_updated; *keys = buffer.keys; *progress = buffer.progress; return 1; @@ -137,12 +161,13 @@ void receiveChildInfo(void) { if (server.child_info_pipe[0] == -1) return; size_t cow; + monotime cow_updated; size_t keys; double progress; childInfoType information_type; /* Drain the pipe and update child info so that we get the final message. */ - while (readChildInfo(&information_type, &cow, &keys, &progress)) { - updateChildInfo(information_type, cow, keys, progress); + while (readChildInfo(&information_type, &cow, &cow_updated, &keys, &progress)) { + updateChildInfo(information_type, cow, cow_updated, keys, progress); } } |