Make IO_SIZE compile-time configurable, convert comment to compile-time check, fix grammar #3726
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This #define is duplicated in the submodule How are changes in Is there an existing process? Should I open a parallel PR for that? |
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If the server is to make IO_SIZE configurable, we need to avoid either redefining it, or defining it to be different. See: MariaDB/server#3726 Signed-off-by: Eric Herman <[email protected]>
I've created a draft PR: mariadb-corporation/mariadb-connector-c#265 I think I will create an MDEV for this work, as it crosses repository boundaries. |
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include/my_global.h
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| #define IO_SIZE 4096U | ||
| #endif | ||
| #if ((IO_SIZE <= 0) || ((IO_SIZE % 512) != 0) || ((IO_SIZE & (IO_SIZE-1)) != 0)) |
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This can be shortened to
#if IO_SIZE < 512 || (IO_SIZE & (IO_SIZE - 1))
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Yes. And with the text in the #error, I agree that it remains clear-enough. I shall adjust it.
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If the server is to make IO_SIZE configurable, we need to avoid either redefining it, or defining it to be different. See: MariaDB/server#3726 Signed-off-by: Eric Herman <[email protected]>
By converting the text describing the constraints of the constant to a compile-time check, this enables us to make IO_SIZE configurable. It should be noted that this #define is duplicated in the submodule libmariadb in the include/ma_global.h file. Signed-off-by: Eric Herman <[email protected]>
Making mariadb's IO_SIZE compile-time configurable enables more straight-forward investigation of the performance implications of having an IO_SIZE which is different than the memory page size. The default IO_SIZE of 4096 as defined in include/my_global.h and also in libmariadb's include/ma_global.h matches to the memory page size of most systems. Larger page sizes are widely supported, called "huge pages" in Linux, "superpages" in FreeBSD, and "large pages" in MS Windows. On POSIX systems, obtaining the page size can be done via: page_size= sysconf(_SC_PAGESIZE); On Windows: SYSTEM_INFO si; GetSystemInfo(&si); page_size= si.dwPageSize; In https://jira.mariadb.org/browse/MDEV-35740 Marko highlights that there are vastly different uses of IO_SIZE. This "one size fits all" nature of IO_SIZE is not ideal, future work could split this into separate constants based upon usage. Note that libmariadb's include/ma_global.h should also be adjusted to avoid a double #define of IO_SIZE and to ensure they are defined to be the same. See: mariadb-corporation/mariadb-connector-c#265 Signed-off-by: Eric Herman <[email protected]>
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The server's definition of IO_SIZE is re-used here in the client for network buffer alignment, however IO_SIZE is used in the server for many different things and the client's buffer alignment is not related to many of those uses. If the server is to make IO_SIZE configurable, we need to avoid either redefining it, or defining it to be different. By creating a specific define for this, we avoid redfine and clarify the code. See: MariaDB/server#3726 Signed-off-by: Eric Herman <[email protected]>
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The server's definition of IO_SIZE is re-used here in the client for network buffer alignment, however IO_SIZE is used in the server for many different things and the client's buffer alignment is not related to many of those uses. If the server is to make IO_SIZE configurable, we need to avoid either redefining it, or defining it to be different. By creating a specific define for this, we avoid redfine and clarify the code. See: MariaDB/server#3726 Signed-off-by: Eric Herman <[email protected]>
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There is no JIRA for this simple refactoring.
Description
Making mariadb's IO_SIZE compile-time configurable enables more straight-forward investigation of the performance implications of having an IO_SIZE which is different than the memory page size.
By converting the text describing the constraints of the constant to a compile-time check, this enables us to make IO_SIZE configurable.
It should be noted that this #define is duplicated in the submodule libmariadb in the include/ma_global.h file.
Release Notes
Release notes might include the ability to define IO_SIZE to be a value other than 4096.
How can this PR be tested?
First, ensure that libmariadb is patched to
#ifndefguard the#define IO_SIZE( see: mariadb-corporation/mariadb-connector-c#265 ).Next, add different values via
cmakelike-DIO_SIZE=8192to see a larger value, or like-DIO_SIZE=4000to see it fail with a compile-time error.As this is a compile-time option this does not lend itself to automated testing.
Basing the PR against the correct MariaDB version
mainbranch.PR quality check