1f641d9410
Found a read performance issue when linux kernel page size is 64KB. If linux kernel page size is 64KB and mount options cache=strict & vers=2.1+, it does not support cifs_readpages(). Instead, it is using cifs_readpage() and cifs_read() with maximum read IO size 16KB, which is much slower than read IO size 1MB when negotiated SMB 2.1+. Since modern SMB server supported SMB 2.1+ and Max Read Size can reach more than 64KB (for example 1MB ~ 8MB), this patch check max_read instead of maxBuf to determine whether server support readpages() and improve read performance for page size 64KB & cache=strict & vers=2.1+, and for SMB1 it is more cleaner to initialize server->max_read to server->maxBuf. The client is a linux box with linux kernel 4.2.8, page size 64KB (CONFIG_ARM64_64K_PAGES=y), cpu arm 1.7GHz, and use mount.cifs as smb client. The server is another linux box with linux kernel 4.2.8, share a file '10G.img' with size 10GB, and use samba-4.7.12 as smb server. The client mount a share from the server with different cache options: cache=strict and cache=none, mount -tcifs //<server_ip>/Public /cache_strict -overs=3.0,cache=strict,username=<xxx>,password=<yyy> mount -tcifs //<server_ip>/Public /cache_none -overs=3.0,cache=none,username=<xxx>,password=<yyy> The client download a 10GbE file from the server across 1GbE network, dd if=/cache_strict/10G.img of=/dev/null bs=1M count=10240 dd if=/cache_none/10G.img of=/dev/null bs=1M count=10240 Found that cache=strict (without patch) is slower read throughput and smaller read IO size than cache=none. cache=strict (without patch): read throughput 40MB/s, read IO size is 16KB cache=strict (with patch): read throughput 113MB/s, read IO size is 1MB cache=none: read throughput 109MB/s, read IO size is 1MB Looks like if page size is 64KB, cifs_set_ops() would use cifs_addr_ops_smallbuf instead of cifs_addr_ops, /* check if server can support readpages */ if (cifs_sb_master_tcon(cifs_sb)->ses->server->maxBuf < PAGE_SIZE + MAX_CIFS_HDR_SIZE) inode->i_data.a_ops = &cifs_addr_ops_smallbuf; else inode->i_data.a_ops = &cifs_addr_ops; maxBuf is came from 2 places, SMB2_negotiate() and CIFSSMBNegotiate(), (SMB2_MAX_BUFFER_SIZE is 64KB) SMB2_negotiate(): /* set it to the maximum buffer size value we can send with 1 credit */ server->maxBuf = min_t(unsigned int, le32_to_cpu(rsp->MaxTransactSize), SMB2_MAX_BUFFER_SIZE); CIFSSMBNegotiate(): server->maxBuf = le32_to_cpu(pSMBr->MaxBufferSize); Page size 64KB and cache=strict lead to read_pages() use cifs_readpage() instead of cifs_readpages(), and then cifs_read() using maximum read IO size 16KB, which is much slower than maximum read IO size 1MB. (CIFSMaxBufSize is 16KB by default) /* FIXME: set up handlers for larger reads and/or convert to async */ rsize = min_t(unsigned int, cifs_sb->rsize, CIFSMaxBufSize); Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com> Signed-off-by: Jones Syue <jonessyue@qnap.com> Signed-off-by: Steve French <stfrench@microsoft.com> |
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| arch | ||
| block | ||
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| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
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| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
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| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.