glibc/benchtests, branch master

Benchtests: Remove broken walk benchmarks

2024-06-21T13:41:42Z

The walk benchmarks don't measure anything useful - memory is not initialized properly so doing a single walk in 32MB just measures reading the 4KB zero page for reads and clear_page overhead for writes. The memset variants don't even manage to do a walk in the 32MB region due to using incorrect pointer increments... Neither is it clear why it is walking backwards since this won't confuse modern prefetchers. If you fix the benchmark and print the bandwidth, the results are identical for all sizes larger than ~1KB since it is just testing memory bandwidth of a single 32MB block. This case is already tested by the large benchmark, so overall it doesn't seem useful to keep these. Reviewed-by: Carlos O'Donell

Modernize and fix doc’s “Date and Time” (BZ 31876)

2024-06-15T15:53:50Z

POSIX.1-2024 (now official) specifies tm_gmtoff and tm_zone. This is a good time to update the manual’s “Date and Time” chapter so I went through it, fixed some outdated stuff that had been in there for decades, and improved it to match POSIX.1-2024 better and to clarify some implementation-defined behavior. Glibc already conforms to POSIX.1-2024 in these matters, so this is merely a documentation change. * manual/examples/strftim.c: Use snprintf instead of now-deprecated function asctime. Check for localtime failure. Simplify by using puts instead of fputs. Prefer ‘buf, sizeof buf’ to less-obvious ‘buffer, SIZE’. * manual/examples/timespec_subtract.c: Modernize to use struct timespec not struct timeval, and rename from timeval_subtract.c. All uses changed. Check for overflow. Do not check for negative return value, which ought to be OK since negative time_t is OK. Use GNU indenting style. * manual/time.texi: Document CLOCKS_PER_SEC, TIME_UTC, timespec_get, timespec_getres, strftime_l. Document the storage lifetime of tm_zone and of tzname. Caution against use of tzname, timezone and daylight, saying that these variables have unspecified values when TZ is geographic. This is what glibc actually does (contrary to what the manual said before this patch), and POSIX is planned to say the same thing . Also say that directly accessing the variables is not thread-safe. Say that localtime_r and ctime_r don’t necessarily set time zone state. Similarly, in the tzset documentation, say that it is called by ctime, localtime, mktime, strftime, not that it is called by all time conversion functions that depend on the time zone. Say that tm_isdst is useful mostly just for mktime, and that other uses should prefer tm_gmtoff and tm_zone instead. Do not say that strftime ignores tm_gmtoff and tm_zone, because it doesn’t do that. Document what gmtime does to tm_gmtoff and tm_zone. Say that the asctime, asctime_r, ctime, and ctime_r are now deprecated and/or obsolescent, and that behavior is undefined if the year is < 1000 or > 9999. Document strftime before these now-obsolescent functions, so that readers see the useful function first. Coin the terms “geographical format” and “proleptic format” for the two main formats of TZ settings, to simplify exposition. Use this wording consistently. Update top-level proleptic syntax to match POSIX.1-2024, which glibc already implements. Document the angle-bracket quoted forms of time zone abbreviations in proleptic TZ. Say that time zone abbreviations can contain only ASCII alphanumerics, ‘+’, and ‘-’. Document what happens if the proleptic form specifies a DST abbreviation and offset but omits the rules. POSIX says this is implementation-defined so we need to document it. Although this documentation mentions ‘posixrules’ tersely, we need to rethink ‘posixrules’ since I think it stops working after 2038. Clarify wording about TZ settings beginning with ‘;’. Say that timegm is in ISO C (as of C23). Say that POSIX.1-2024 removed gettimeofday. Say that tm_gmtoff and tm_zone are extensions to ISO C, which is clearer than saying they are invisible in a struct ISO C enviroment, and gives us more wiggle room if we want to make them visible in strict ISO C, something that ISO C allows. Drop mention of old standards like POSIX.1c and POSIX.2-1992 in the text when the history is so old that it’s no longer useful in a general-purpose manual. Define Coordinated Universal Time (UTC), time zone, time zone ruleset, and POSIX Epoch, and use these phrases more consistently. Improve TZ examples to show more variety, and to reflect current practice and timestamps. Remove obsolete example about Argentina. Add an example for Ireland. Don’t rely on GCC extensions when explaining ctime_r. Do not say that difftime produces the mathematically correct result, since it might be inexact. For clock_t don’t say “as in the example above” when there is no such example, and don’t say that casting to double works “properly and consistently no matter what”, as it suffers from rounding and overflow. Don’t say broken-down time is not useful for calculations; it’s merely painful. Say that UTC is not defined before 1960. Rename Time Zone Functions to Time Zone State. All uses changed. Update Internet RFC 822 → 5322, 1305 → 5905. Drop specific years of ISO 8601 as they don’t matter. Minor style changes: @code{"..."} → @t{"..."} to avoid overquoting in info files, @code → @env for environment variables, Daylight Saving Time → daylight saving time, white space → whitespace, prime meridian → Prime Meridian.

benchtests: Add fclose benchmark

2024-05-16T15:12:59Z

Measure duration of 100 fclose calls after opening 1 million FILEs. Signed-off-by: H.J. Lu Reviewed-by: Carlos O'Donell

benchtests: Add difficult strstr needle for bruteforce algorithms

2024-04-24T17:25:46Z

Add another difficult needle to strstr that clearly shows the quadratic complexity of bruteforce algorithms. Reviewed-by: Adhemerval Zanella

benchtests: Add random() benchmark

2024-04-18T13:30:21Z

Add a simple benchmark to measure the overhead of internal libc locks in the random() implementation on both single- and multi-threaded cases. This relies on the implementation of random using internal locks to access shared global data, and that the runtime uses multi-threaded locking once a thread has been created (even after it finishes). Reviewed-by: Adhemerval Zanella

benchtests: Improve benchtests for strstr

2024-04-01T16:52:00Z

Use same strategy as bench-strstr.c (93eebae5168e5cf2 and 80b2bfb53504) and use json_ctx for output to help standardize format across all benchtests. Reviewed-by: Arjun Shankar

benchtests: Add more benchtests for rounding functions.

2024-02-23T11:50:00Z

This patch adds more benchtests for rounding functions. The double inputs are copied from trunc-inputs, the float inputs are copied from truncf-inputs. and the rintf is copied from rint-inputs. Reviewed-by: Adhemerval Zanella

Benchtests: Increase benchmark iterations

2024-01-12T16:00:28Z

Increase benchmark iterations for math and vector math functions to improve timing accuracy. Vector math benchmarks now take 1-3 seconds on a modern CPU. Reviewed-by: Adhemerval Zanella

Update copyright dates with scripts/update-copyrights

2024-01-01T18:53:40Z

benchtests: fix warn unused result

2023-06-22T04:21:19Z

Few tests needed to properly check for asprintf and system calls return values with _FORTIFY_SOURCE enabled. Reviewed-by: Siddhesh Poyarekar