We add a page to the page cache using add_to_page_cache_lru based on the following assumptions
READ MISS - So add an entry
no_cached_page - so we need to create one from
do_generic_file_read - during a file read operation
page_cache_read - calls add_to_page_cache_lru
CREATE A PAGE
struct page *__page_cache_alloc(gfp_t gfp)
page has flags which identify if dirty or free
Writes
add_to_page_cache
writepage / writepages
set_page_dirty_buffers
do_generic_mapping_read - ASYNC read of pages in readahed?
__block_write_full_page
READ
find_get_pages
mark_page_accessed() for measuring cache accesses
mark_buffer_dirty() for measuring cache writes
add_to_page_cache_lru() for measuring page additions
account_page_dirtied() for measuring page dirties
(mark_page_accessed - mark_buffer_dirty) & misses = (add_to_page_cache_lru - account_page_dirtied),
from this I then work out the hit ratio etc. Is there any other key functions I should be tracing?
add_to_page_cache_lru
lru_cache_add
swap.c
filemap.c
vmscan.c
Functions used
lru_cache_add_active_or_unevictable
add_to_page_cache_lru
putback_lru_page
So best use lru_cache_add for additions.
account_page_dirtied() for measuring page dirties
set_page_dirty - calls above
__set_page_dirty_nobuffers - calls above also
mark_buffer_dirty() for measuring cache writes - this calls __set_page_dirty ( are we getting twice the calls here? )
mark_page_accessed - calls SetPageActive
On Thu, Dec 10, 2015 at 9:42 AM, Allan McAleavy <allan.mcaleavy@xxxxxxxxx> wrote:
Hi Folks,I am working on a rewrite of Brendan Greggs original cachestat (ftrace) script into bcc. What I was looking for was a steer in the right direction for what functions to trace. At present I trace the following.add_to_page_cache_lruaccount_page_dirtiedmark_page_accessedmark_buffer_dirtyWhere total = (mark_page_accessed - mark_buffer_dirty) & misses = (add_to_page_cache_lru - account_page_dirtied), from this I then work out the hit ratio etc. Is there any other key functions I should be tracing?Thanks