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Merge pull request #3154 from terrelln/rsyncable-speed-fix

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Remove expensive assert in --rsyncable hot loop
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Nick Terrell 2022-06-06 16:07:20 -07:00 committed by GitHub
commit 802ad778cc
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1 changed files with 8 additions and 1 deletions
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lib/compress/zstdmt_compress.c
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@ -1761,17 +1761,24 @@ findSynchronizationPoint(ZSTDMT_CCtx const* mtctx, ZSTD_inBuffer const input)
* then a block will be emitted anyways, but this is okay, since if we * then a block will be emitted anyways, but this is okay, since if we
* are already synchronized we will remain synchronized. * are already synchronized we will remain synchronized.
*/ */
assert(pos < RSYNC_LENGTH || ZSTD_rollingHash_compute(istart + pos - RSYNC_LENGTH, RSYNC_LENGTH) == hash);
for (; pos < syncPoint.toLoad; ++pos) { for (; pos < syncPoint.toLoad; ++pos) {
BYTE const toRemove = pos < RSYNC_LENGTH ? prev[pos] : istart[pos - RSYNC_LENGTH]; BYTE const toRemove = pos < RSYNC_LENGTH ? prev[pos] : istart[pos - RSYNC_LENGTH];
assert(pos < RSYNC_LENGTH || ZSTD_rollingHash_compute(istart + pos - RSYNC_LENGTH, RSYNC_LENGTH) == hash); /* This assert is very expensive, and Debian compiles with asserts enabled.
* So disable it for now. We can get similar coverage by checking it at the
* beginning & end of the loop.
* assert(pos < RSYNC_LENGTH || ZSTD_rollingHash_compute(istart + pos - RSYNC_LENGTH, RSYNC_LENGTH) == hash);
*/
hash = ZSTD_rollingHash_rotate(hash, toRemove, istart[pos], primePower); hash = ZSTD_rollingHash_rotate(hash, toRemove, istart[pos], primePower);
assert(mtctx->inBuff.filled + pos >= RSYNC_MIN_BLOCK_SIZE); assert(mtctx->inBuff.filled + pos >= RSYNC_MIN_BLOCK_SIZE);
if ((hash & hitMask) == hitMask) { if ((hash & hitMask) == hitMask) {
syncPoint.toLoad = pos + 1; syncPoint.toLoad = pos + 1;
syncPoint.flush = 1; syncPoint.flush = 1;
++pos; /* for assert */
break; break;
} }
} }
assert(pos < RSYNC_LENGTH || ZSTD_rollingHash_compute(istart + pos - RSYNC_LENGTH, RSYNC_LENGTH) == hash);
return syncPoint; return syncPoint;
} }