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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
