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Do not cache readahead-pages in the OS cache.

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Summary:
When posix_fadvise(offset, offset) is usedm it frees up only those
pages in that specified range. But the filesystem could have done some
read-aheads and those get cached in the OS cache.

Do not cache readahead-pages in the OS cache.

Test Plan: run db_bench benchmark.

Reviewers: vamsi, heyongqiang

Reviewed By: heyongqiang

Differential Revision: https://reviews.facebook.net/D5379
This commit is contained in:
Dhruba Borthakur 2012-09-13 10:10:51 -07:00
parent 7ecc5d4ad5
commit 4028ae7d31
1 changed files with 3 additions and 1 deletions
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4
util/env_posix.cc
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@ -94,7 +94,9 @@ class PosixRandomAccessFile: public RandomAccessFile {
s = IOError(filename_, errno);
}
if (!useOsBuffer) {
posix_fadvise(fd_, offset, n, POSIX_FADV_DONTNEED); // free OS pages
// we need to fadvise away the entire range of pages because
// we do not want readahead pages to be cached.
posix_fadvise(fd_, 0, 0, POSIX_FADV_DONTNEED); // free OS pages
}
return s;
}