On Thu 22-06-17 09:58:17, Nikolay Borisov wrote: > > > On 22.06.2017 09:44, Michal Hocko wrote: > > On Tue 20-06-17 18:14:28, Nikolay Borisov wrote: > >> Currently there are a multiple files with the following code: > >> #define K(x) ((x) << (PAGE_SHIFT - 10)) > >> ... some code.. > >> #undef K > >> > >> This is mainly used to print out some memory-related statistics, where X is > >> given in pages and the macro just converts it to kilobytes. In the future > >> there is going to be more macros since there are intention to introduce > >> byte-based memory counters [1]. This could lead to proliferation of > >> multiple duplicated definition of various macros used to convert a quantity > >> from one unit to another. Let's try and consolidate such definition in the > >> mm.h header since currently it's being included in all files which exhibit > >> this pattern. Also let's rename it to something a bit more verbose. > >> > >> This patch doesn't introduce any functional changes > >> > >> [1] https://patchwork.kernel.org/patch/9395205/ > >> > >> Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx> > >> --- > >> arch/tile/mm/pgtable.c | 2 -- > >> drivers/base/node.c | 66 ++++++++++++++++++------------------- > >> include/linux/mm.h | 2 ++ > >> kernel/debug/kdb/kdb_main.c | 3 +- > >> mm/backing-dev.c | 22 +++++-------- > >> mm/memcontrol.c | 17 +++++----- > >> mm/oom_kill.c | 19 +++++------ > >> mm/page_alloc.c | 80 ++++++++++++++++++++++----------------------- > >> 8 files changed, 100 insertions(+), 111 deletions(-) > > > > Those macros are quite trivial and we do not really save much code while > > this touches a lot of code potentially causing some conflicts. So do we > > really need this? I am usually very keen on removing duplication but > > this doesn't seem to be worth all the troubles IMHO. > > > > There are 2 problems I see: > > 1. K is in fact used for other macros than converting pages to kbytes. > Simple grep before my patch is applied yields the following: > > arch/tile/mm/pgtable.c:#define K(x) ((x) << (PAGE_SHIFT-10)) > arch/x86/crypto/serpent-sse2-i586-asm_32.S:#define K(x0, x1, x2, x3, x4, i) \ > crypto/serpent_generic.c:#define K(x0, x1, x2, x3, i) ({ \ > drivers/base/node.c:#define K(x) ((x) << (PAGE_SHIFT - 10)) > drivers/net/hamradio/scc.c:#define K(x) kiss->x > include/uapi/linux/keyboard.h:#define K(t,v) (((t)<<8)|(v)) > kernel/debug/kdb/kdb_main.c:#define K(x) ((x) << (PAGE_SHIFT - 10)) > mm/backing-dev.c:#define K(x) ((x) << (PAGE_SHIFT - 10)) > mm/backing-dev.c:#define K(pages) ((pages) << (PAGE_SHIFT - 10)) > mm/memcontrol.c:#define K(x) ((x) << (PAGE_SHIFT-10)) > mm/oom_kill.c:#define K(x) ((x) << (PAGE_SHIFT-10)) > mm/page_alloc.c:#define K(x) ((x) << (PAGE_SHIFT-10)) > > > Furthermore, I intend on sending another patchset which introduces 2 more macros: > drivers/base/node.c:#define BtoK(x) ((x) >> 10) > drivers/video/fbdev/intelfb/intelfb.h:#define BtoKB(x) ((x) / 1024) > mm/backing-dev.c:#define BtoK(x) ((x) >> 10) > mm/page_alloc.c:#define BtoK(x) ((x) >> 10) > > fs/fs-writeback.c:#define BtoP(x) ((x) >> PAGE_SHIFT) > include/trace/events/writeback.h:#define BtoP(x) ((x) >> PAGE_SHIFT) > mm/page_alloc.c:#define BtoP(x) ((x) >> PAGE_SHIFT) > > As you can see this ends up in spreading those macros. Ideally > they should be in a header which is shared among all affected > files. This was inspired by the feedback that Tejun has given > here: https://patchwork.kernel.org/patch/9395205/ and I believe > he is right. Fair enough, if this is part of a larger work then I would incline to do all of them in a single series. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
