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package.c (readPackageHeaders): use posix_fadvise(2) to disable readahead

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This commit is contained in:
Alexey Tourbin 2009-05-07 06:24:32 +04:00
parent af944d993e
commit 66b17f5fd5
1 changed files with 10 additions and 0 deletions
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10
lib/package.c
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@ -244,12 +244,22 @@ static rpmRC readPackageHeaders(FD_t fd,
/*@modifies fd, *leadPtr, *sigs, *hdrPtr @*/
{
struct stat sb;
int readahead_off = 0;
/* if fd points to a socket, pipe, etc, sb.st_size is *always* zero */
if (fstat(Fileno(fd), &sb) == 0 && S_ISREG(sb.st_mode)) {
if (sb.st_size < sizeof(struct rpmlead))
return 1;
/* Typical header size is 4-16K, and default readahead is 128K.
* When scanning a large number of packages (with e.g. rpmquery),
* readahead might cause negative effects on the buffer cache. */
if (sb.st_size > /* page size */ 4096)
if (posix_fadvise(Fileno(fd), 0, 0, POSIX_FADV_RANDOM) == 0)
readahead_off = 1;
}
rpmRC rc = do_readPackageHeaders(fd, leadPtr, sigs, hdrPtr);
/* re-enable readahead for cpio */
if (readahead_off)
posix_fadvise(Fileno(fd), 0, 0, POSIX_FADV_NORMAL);
return rc;
}