[PATCH v2 0/8] Handle mmaped regions in cache

[Michael Holzheu]

Hello Petr,

With your patch we get 5-10 percent performance improvement on s390.

Two examples:

$ time ./makedumpfile  -d 31 /proc/vmcore  /dev/null -f

                  user   sys  = total
=====================================
With patches      0.156  0.248  0.404
Without patches   0.168  0.274  0.442  <- No idea why we save system time?

$ time ./makedumpfile  -d 0 /proc/vmcore  /dev/null -f

                  user   sys  = total
=====================================
With patches      0.683  0.020  0.703
Without patches   0.714  0.019  0.733

Regards
Michael

On Fri, 6 Mar 2015 15:03:12 +0100
Petr Tesarik <ptesarik at suse.cz> wrote:

> Because all pages must go into the cache, data is unnecessarily
> copied from mmapped regions to cache. Avoid this copying by storing
> the mmapped regions directly in the cache.
> 
> First, the cache code needs a clean up clarification of the concept,
> especially the meaning of the pending list (allocated cache entries
> whose content is not yet valid).
> 
> Second, the cache must be able to handle differently sized objects
> so that it can store individual pages as well as mmapped regions.
> 
> Last, the cache eviction code must be extended to allow either
> reusing the read buffer or unmapping the region.
> 
> Changelog:
>   v2: cache cleanup _and_ actuall mmap implementation
>   v1: only the cache cleanup
> 
> Petr Tesarik (8):
>   cache: get rid of search loop in cache_add()
>   cache: allow to return a page to the pool
>   cache: do not allocate from the pending list
>   cache: add hit/miss statistics to the final report
>   cache: allocate buffers in one big chunk
>   cache: allow arbitrary size of cache entries
>   cache: store mapped regions directly in the cache
>   cleanup: remove unused page_is_fractional
> 
>  cache.c        |  81 +++++++++++++++++----------------
>  cache.h        |  16 +++++--
>  elf_info.c     |  16 -------
>  elf_info.h     |   2 -
>  makedumpfile.c | 138 ++++++++++++++++++++++++++++++++++-----------------------
>  5 files changed, 138 insertions(+), 115 deletions(-)
>