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zlib: slim down zlib_deflate() workspace when possible

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Instead of always creating a huge (268K) deflate_workspace with the
maximum compression parameters (windowBits=15, memLevel=8), allow the
caller to obtain a smaller workspace by specifying smaller parameter
values.

For example, when capturing oops and panic reports to a medium with
limited capacity, such as NVRAM, compression may be the only way to
capture the whole report.  In this case, a small workspace (24K works
fine) is a win, whether you allocate the workspace when you need it (i.e.,
during an oops or panic) or at boot time.

I've verified that this patch works with all accepted values of windowBits
(positive and negative), memLevel, and compression level.

Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jim Keniston 2011-03-22 16:35:12 -07:00 • committed by Linus Torvalds
parent b12d125969
commit 565d76cb7d
9 changed files with 71 additions and 23 deletions
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11
include/linux/zlib.h
View file

@ -179,11 +179,16 @@ typedef z_stream *z_streamp;
/* basic functions */
extern int zlib_deflate_workspacesize (void);
extern int zlib_deflate_workspacesize (int windowBits, int memLevel);
/*
Returns the number of bytes that needs to be allocated for a per-
stream workspace. A pointer to this number of bytes should be
returned in stream->workspace before calling zlib_deflateInit().
stream workspace with the specified parameters. A pointer to this
number of bytes should be returned in stream->workspace before
you call zlib_deflateInit() or zlib_deflateInit2(). If you call
zlib_deflateInit(), specify windowBits = MAX_WBITS and memLevel =
MAX_MEM_LEVEL here. If you call zlib_deflateInit2(), the windowBits
and memLevel parameters passed to zlib_deflateInit2() must not
exceed those passed here.
*/
/*