unlinking...and calloc

--MimeMultipartBoundary
Content-type: text/plain; charset=US-ASCII
Content-transfer-encoding: 7BIT

 Hi,

 squid has sort of cache for unused fileno's that is fixed at 128. Same sort of cache
 and about same size is unused files in filemap.c.
 unlinking is expensive, and main squid process does unlink() when any of these
 unused-file-caches overflows. sorta bad, I've seen unlink() calls that takes more
 than 100mSec to complete, and thats on RAID5 system with 6 disks. When cache is
 filled and is working between its high/low watermarks, these unlinks become pretty
 usual, especially on a busy cache.

 Therefore, I'd suggest to make these arrays that cache recently released filenos
 bigger, and resizable during runtime. Perhaps best criteria to chose their size
 is balance between max possible number of releases and max possible number of new
 allocations - that would be tied to availbale no of FD-s. for NOVM version, I guess,
 it would be 1/4 of available FD's.
 Reuse of recenlty released files is a performance improvement, as it changes
 unlink()-sync-open(wr) into single open(wr|trunc) on a "warm" and OS-cached file/inode.

 btw, why unlink at all, why not truncate and leave it there?

 and a question.
 Can you guys explain me what happens when I ptr=calloc("1 chunk", "of say 16MB")
 work on it, then free(). process SIZE does not drop after free(). Feels like libmalloc
 sets freed memory aside in hope that it would be reused. What about the case that
 malloc of this size never happens again? Would this amount of VM be simply wasted, or
 is libmalloc clever enough to reuse this memory for smaller chunks? (eg. gnumalloc?)
 Would it be more clever to code it to ptr=calloc("say 2048 chunks","of 8KB each"),
 is there any difference? Does libmalloc keep track of such allocation differently?

 ----------------------------------------------------------------------
  Andres Kroonmaa mail: andre@online.ee
  Network Manager
  Organization: MicroLink Online Tel: 6308 909
  Tallinn, Sakala 19 Pho: +372 6308 909
  Estonia, EE0001 http://www.online.ee Fax: +372 6308 901
 ----------------------------------------------------------------------

--MimeMultipartBoundary--
Received on Tue Jul 29 2003 - 13:15:45 MDT