Hello Jingbai, >> This patch intends to reduce unnecessary memory copy in compressing memory >> blocks. >> >> old logic like this: >> compress(buf_out, &size_out, buf, size); >> ... >> memcpy(buf, buf_out, pd.size); >> ... >> write_cache(cd_page, buf, pd.size) >> >> new logic: >> compress(buf_out, &size_out, buf, size); >> ... >> if (compressed?) >> write_cache(cd_page, buf_out, pd.size) >> else >> write_cache(cd_page, buf, pd.size) >> >> This occurs for each single page, so by the new logic it can reduce a lot of >> unnecessary memcpy() on machines with huge memory. >> This patch wasn't expected to improve the kdump performance dramatically due >> to >> the memory copy operations on modern processors are pretty fast. >> > >Now /proc/vmcore has zero copy mechanism with mmap(), but now >makedumpfile still uses buffers some places in makedumpfile to keep >changes as less as possible for ease of maintainance. I think ease of >maintainance is important, so I don't think we should soon totally >remove copy in makedumpfile. We should first benchmark where can be >improved very much by just removing copy and then should decide where >to optimize. > >OTOH, this patch also seems to be a kind of clean-up patch. Even if >amount of improvement is a little, I don't object this patch; of >course, then patch description should say it's rather cleanup patch >than optimization.
I have no additional comments, so please send the v2 patch. Thanks Atsushi Kumagai >> >> Signed-off-by: Jingbai Ma <[email protected]> >> --- >> makedumpfile.c | 24 ++++++++++++++---------- >> 1 files changed, 14 insertions(+), 10 deletions(-) >> >> diff --git a/makedumpfile.c b/makedumpfile.c >> index 23251a1..80f76cf 100644 >> --- a/makedumpfile.c >> +++ b/makedumpfile.c >> @@ -6245,7 +6245,6 @@ write_kdump_pages(struct cache_data *cd_header, struct >> cache_data *cd_page) >> && (size_out < info->page_size)) { >> pd.flags = DUMP_DH_COMPRESSED_ZLIB; >> pd.size = size_out; >> - memcpy(buf, buf_out, pd.size); >> #ifdef USELZO >> } else if (info->flag_lzo_support >> && (info->flag_compress & DUMP_DH_COMPRESSED_LZO) >> @@ -6255,7 +6254,6 @@ write_kdump_pages(struct cache_data *cd_header, struct >> cache_data *cd_page) >> && (size_out < info->page_size)) { >> pd.flags = DUMP_DH_COMPRESSED_LZO; >> pd.size = size_out; >> - memcpy(buf, buf_out, pd.size); >> #endif >> #ifdef USESNAPPY >> } else if ((info->flag_compress & DUMP_DH_COMPRESSED_SNAPPY) >> @@ -6267,7 +6265,6 @@ write_kdump_pages(struct cache_data *cd_header, struct >> cache_data *cd_page) >> && (size_out < info->page_size)) { >> pd.flags = DUMP_DH_COMPRESSED_SNAPPY; >> pd.size = size_out; >> - memcpy(buf, buf_out, pd.size); >> #endif >> } else { >> pd.flags = 0; >> @@ -6286,8 +6283,13 @@ write_kdump_pages(struct cache_data *cd_header, >> struct cache_data *cd_page) >> /* >> * Write the page data. >> */ >> - if (!write_cache(cd_page, buf, pd.size)) >> - goto out; >> + if (pd.flags == 0) { >> + if (!write_cache(cd_page, buf, pd.size)) >> + goto out; >> + } else { >> + if (!write_cache(cd_page, buf_out, pd.size)) >> + goto out; >> + } >> } > >if (!write_cache(cd_page, pd.flags ? buf_out : buf, pd.size)) > goto out; > >> >> /* >> @@ -6424,7 +6426,6 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, >> struct cache_data *cd_pag >> && (size_out < info->page_size)) { >> pd.flags = DUMP_DH_COMPRESSED_ZLIB; >> pd.size = size_out; >> - memcpy(buf, buf_out, pd.size); >> #ifdef USELZO >> } else if (info->flag_lzo_support >> && (info->flag_compress & DUMP_DH_COMPRESSED_LZO) >> @@ -6434,7 +6435,6 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, >> struct cache_data *cd_pag >> && (size_out < info->page_size)) { >> pd.flags = DUMP_DH_COMPRESSED_LZO; >> pd.size = size_out; >> - memcpy(buf, buf_out, pd.size); >> #endif >> #ifdef USESNAPPY >> } else if ((info->flag_compress & DUMP_DH_COMPRESSED_SNAPPY) >> @@ -6446,7 +6446,6 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, >> struct cache_data *cd_pag >> && (size_out < info->page_size)) { >> pd.flags = DUMP_DH_COMPRESSED_SNAPPY; >> pd.size = size_out; >> - memcpy(buf, buf_out, pd.size); >> #endif >> } else { >> pd.flags = 0; >> @@ -6465,8 +6464,13 @@ write_kdump_pages_cyclic(struct cache_data >> *cd_header, struct cache_data *cd_pag >> /* >> * Write the page data. >> */ >> - if (!write_cache(cd_page, buf, pd.size)) >> - goto out; >> + if (pd.flags == 0) { >> + if (!write_cache(cd_page, buf, pd.size)) >> + goto out; >> + } else { >> + if (!write_cache(cd_page, buf_out, pd.size)) >> + goto out; >> + } >> } > >Similaly. > >> >> ret = TRUE; >> > >Thanks. >HATAYAMA, Daisuke _______________________________________________ kexec mailing list [email protected] http://lists.infradead.org/mailman/listinfo/kexec
