• Andrew Morton's avatar
    [PATCH] lru_add_active(): for starting pages on the active list · 228c3d15
    Andrew Morton authored
    This is the first in a series of patches which tune up the 2.5
    performance under heavy swap loads.
    
    Throughput on stupid swapstormy tests is increased by 1.5x to 3x.
    Still about 20% behind 2.4 with multithreaded tests.  That is not
    easily fixable - the virtual scan tends to apply a form of load
    control: particular processes are heavily swapped out so the others can
    get ahead.  With 2.5 all processes make very even progress and much
    more swapping is needed.  It's on par with 2.4 for single-process
    swapstorms.
    
    
    In this patch:
    
    The code which tries to start mapped pages out on the active list
    doesn't work very well.  It uses an "is it mapped into pagetables"
    test.  Which doesn't work for, say, swap readahead pages.  They are not
    mapped into pagetables when they are spilled onto the LRU.
    
    So create a new `lru_cache_add_active()' function for deferred addition
    of pages to their active list.
    
    Also move mark_page_accessed() from filemap.c to swap.c where all
    similar functions live.  And teach it to not try to move pages which
    are in the deferred-addition list onto the active list.  That won't
    work, and it's bogusly clearing PageReferenced in that case.
    
    The deferred-addition lists are a pest.  But lru_cache_add used to be
    really expensive in sime workloads on some machines.  Must persist.
    228c3d15
swap.c 8.16 KB