From 247d2a734b0434e0f461902f64d32cb6e587709c Mon Sep 17 00:00:00 2001 From: "zhaozhao.zz" Date: Tue, 4 Sep 2018 00:02:18 +0800 Subject: [PATCH] networking: optimize parsing large bulk greater than 32k If we are going to read a large object from network try to make it likely that it will start at c->querybuf boundary so that we can optimize object creation avoiding a large copy of data. But only when the data we have not parsed is less than or equal to ll+2. If the data length is greater than ll+2, trimming querybuf is just a waste of time, because at this time the querybuf contains not only our bulk. It's easy to reproduce the that: Time1: call `client pause 10000` on slave. Time2: redis-benchmark -t set -r 10000 -d 33000 -n 10000. Then slave hung after 10 seconds. --- src/networking.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/src/networking.c b/src/networking.c index 27c69530..eac94798 100644 --- a/src/networking.c +++ b/src/networking.c @@ -1294,19 +1294,22 @@ int processMultibulkBuffer(client *c) { c->qb_pos = newline-c->querybuf+2; if (ll >= PROTO_MBULK_BIG_ARG) { - size_t qblen; - /* If we are going to read a large object from network * try to make it likely that it will start at c->querybuf * boundary so that we can optimize object creation - * avoiding a large copy of data. */ - sdsrange(c->querybuf,c->qb_pos,-1); - c->qb_pos = 0; - qblen = sdslen(c->querybuf); - /* Hint the sds library about the amount of bytes this string is - * going to contain. */ - if (qblen < (size_t)ll+2) - c->querybuf = sdsMakeRoomFor(c->querybuf,ll+2-qblen); + * avoiding a large copy of data. + * + * But only when the data we have not parsed is less than + * or equal to ll+2. If the data length is greater than + * ll+2, trimming querybuf is just a waste of time, because + * at this time the querybuf contains not only our bulk. */ + if (sdslen(c->querybuf)-c->qb_pos <= (size_t)ll+2) { + sdsrange(c->querybuf,c->qb_pos,-1); + c->qb_pos = 0; + /* Hint the sds library about the amount of bytes this string is + * going to contain. */ + c->querybuf = sdsMakeRoomFor(c->querybuf,ll+2); + } } c->bulklen = ll; }