Re: [Crash-utility] [PATCH] Enhance the "kmem -i" option to properly display the statistics of CACHED

>> Thank you for the comment. >> >> On Wed, Feb 15, 2023 at 1:38 PM HAGIO KAZUHITO(萩尾　一仁) <k-hagio-ab(a)nec.com <mailto:k-hagio-ab@nec.com>> wrote: >> >> On 2023/02/14 23:37, Lianbo Jiang wrote: >> > The "kmem -i" option may output the bogus statistics of CACHED, which >> > might be observed when some extreme situations occur in kernel, such as >> > OOM, disk IO errors, etc. >> > >> > The following result of calculation may be a negative value, refer to >> > the dump_kmeminfo(): >> >    page_cache_size = nr_file_pages - swapper_space_nrpages - buffer_pages; >> > >> > As a result, the negative value will be converted to unsigned long >> > integer, eventually it overflows and gets a big integer. >> > >> >    crash> kmem -i >> >                     PAGES        TOTAL      PERCENTAGE >> >        TOTAL MEM  255314511     973.9 GB         ---- >> >             FREE   533574         2 GB    0% of TOTAL MEM >> >             USED  254780937     971.9 GB   99% of TOTAL MEM >> >           SHARED     1713       6.7 MB    0% of TOTAL MEM >> >          BUFFERS      374       1.5 MB    0% of TOTAL MEM >> >           CACHED     -114  70368744177664 GB  72251060080% of TOTAL MEM >> >                      ^^^^  ^^^^^^^^^^^^^^     ^^^^^^^^^^^^ >> >> I think that this is not very bad output :) because we can notice >> the negative value.  Maybe it's due to future kernel changes. >> >> >> It's true. But it is also easy to mislead users, because it is not clear whether the crash tool >> gave a wrong result. >> >> Actually this issue was observed on the kernel 3.10. >> >> So if you set it to zero, what about emitting an info message? >> >> >> It should be good to have an info message. >> >> +       if (page_cache_size < 0) { >> +               error(INFO, "page_cache_size went negative (%ld), setting to 0\n", >> +                       page_cache_size); >> +               page_cache_size = 0; >> +       } >> >> >> Looks good.