Let user choose larger buffers for IO reading

Simultaneous reading of multiple files through a small one-page buffer
is slow with classic HDDs. Let the user improve it by chosing buffers of
several mebibytes if needed.

[kzak@redhat.com: - tiny changes to coding style
                  - mark buffers static
                  - use xalloc.h]

Signed-off-by: Eduard Bloch <blade@debian.org>
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/misc-utils/hardlink.1.adoc b/misc-utils/hardlink.1.adoc
index 03f6dff78c2e23604726b662448616f56753421c..3d86a441c7e20f761686f37be35411677d9433dc 100644 (file)
--- a/misc-utils/hardlink.1.adoc
+++ b/misc-utils/hardlink.1.adoc
@@ -71,6 +71,12 @@ A regular expression to include files. If the option *--exclude* has been given,
 *-s*, *--minimum-size* _size_::
 The minimum size to consider. By default this is 1, so empty files will not be linked. The _size_ argument may be followed by the multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB").
 
+*-S*, *--buffer-size* _size_::
+The size of read buffer used when comparing file contents (default: 8KiB). This
+costs some additional memory but potentially reduces the amount of seek
+operations and therefore improve performance, especially with mechanic disk
+drives. Optional factor suffixes are supported, like with the *-s* option. This is mostly efficient with other filters (i.e. with *-f* or *-X*) and can be less efficient with *-top* options.
+
 == ARGUMENTS
 
 *hardlink* takes one or more directories which will be searched for files to be linked.

diff --git a/misc-utils/hardlink.c b/misc-utils/hardlink.c
index d49f14a358ea2b59ada8e21109cfd298dd6769aa..a275f2c4247093306ef6ba3db293da7659f12b97 100644 (file)
--- a/misc-utils/hardlink.c
+++ b/misc-utils/hardlink.c
@@ -91,6 +91,10 @@ enum log_level {
        JLOG_VERBOSE2
 };
 
+#ifndef DEF_SCAN_BUFSIZ
+# define DEF_SCAN_BUFSIZ 8192
+#endif
+
 /**
  * struct statistic - Statistics about the file
  * @started: Whether we are post command-line processing
@@ -149,6 +153,7 @@ static struct options {
        unsigned int keep_oldest:1;
        unsigned int dry_run:1;
        uintmax_t min_size;
+       size_t bufsiz;
 } opts = {
        /* default setting */
        .respect_mode = TRUE,
@@ -156,7 +161,8 @@ static struct options {
        .respect_time = TRUE,
        .respect_xattrs = FALSE,
        .keep_oldest = FALSE,
-       .min_size = 1
+       .min_size = 1,
+       .bufsiz = DEF_SCAN_BUFSIZ
 };
 
 /*
@@ -168,6 +174,12 @@ static struct options {
 static void *files;
 static void *files_by_ino;
 
+/*
+ * Temporary buffers for reading file contents
+ */
+static char *buf_a = NULL;
+static char *buf_b = NULL;
+
 /*
  * last_signal
  *
@@ -552,8 +564,6 @@ static int file_contents_equal(const struct file *a, const struct file *b)
 {
        FILE *fa = NULL;
        FILE *fb = NULL;
-       char buf_a[8192];
-       char buf_b[8192];
        int cmp = 0;            /* zero => equal */
        off_t off = 0;          /* current offset */
 
@@ -579,11 +589,11 @@ static int file_contents_equal(const struct file *a, const struct file *b)
                size_t ca;
                size_t cb;
 
-               ca = fread(buf_a, 1, sizeof(buf_a), fa);
+               ca = fread(buf_a, 1, opts.bufsiz, fa);
                if (ca < sizeof(buf_a) && ferror(fa))
                        goto err;
 
-               cb = fread(buf_b, 1, sizeof(buf_b), fb);
+               cb = fread(buf_b, 1, opts.bufsiz, fb);
                if (cb < sizeof(buf_b) && ferror(fb))
                        goto err;
 
@@ -919,6 +929,7 @@ static void __attribute__((__noreturn__)) usage(void)
        fputs(_(" -x, --exclude <regex>      regular expression to exclude files\n"), out);
        fputs(_(" -i, --include <regex>      regular expression to include files/dirs\n"), out);
        fputs(_(" -s, --minimum-size <size>  minimum size for files.\n"), out);
+       fputs(_(" -S, --buffer-size <size>   buffer size for file reading (speedup, using more RAM)\n"), out);
        fputs(_(" -c, --content              compare only file contents, same as -pot\n"), out);
 
        fputs(USAGE_SEPARATOR, out);
@@ -929,6 +940,18 @@ static void __attribute__((__noreturn__)) usage(void)
 }
 
 
+static void init_buffers(size_t bufsiz)
+{
+       buf_a = xmalloc(bufsiz);
+       buf_b = xmalloc(bufsiz);
+}
+
+static void deinit_buffers(void)
+{
+       free(buf_a);
+       free(buf_b);
+}
+
 /**
  * parse_options - Parse the command line options
  * @argc: Number of options
@@ -936,7 +959,7 @@ static void __attribute__((__noreturn__)) usage(void)
  */
 static int parse_options(int argc, char *argv[])
 {
-       static const char optstr[] = "VhvnfpotXcmMOx:i:s:q";
+       static const char optstr[] = "VhvnfpotXcmMOx:i:s:S:q";
        static const struct option long_options[] = {
                {"version", no_argument, NULL, 'V'},
                {"help", no_argument, NULL, 'h'},
@@ -953,6 +976,7 @@ static int parse_options(int argc, char *argv[])
                {"exclude", required_argument, NULL, 'x'},
                {"include", required_argument, NULL, 'i'},
                {"minimum-size", required_argument, NULL, 's'},
+               {"buffer-size", required_argument, NULL, 'S'},
                {"content", no_argument, NULL, 'c'},
                {"quiet", no_argument, NULL, 'q'},
                {NULL, 0, NULL, 0}
@@ -1018,6 +1042,9 @@ static int parse_options(int argc, char *argv[])
                case 's':
                        opts.min_size = strtosize_or_err(optarg, _("failed to parse size"));
                        break;
+               case 'S':
+                       opts.bufsiz = strtosize_or_err(optarg, _("failed to parse size"));
+                       break;
                case 'h':
                        usage();
                case 'V':
@@ -1074,6 +1101,9 @@ int main(int argc, char *argv[])
                errx(EXIT_FAILURE, _("no directory or file specified"));
 
        gettime_monotonic(&stats.start_time);
+
+       init_buffers(opts.bufsiz);
+
        stats.started = TRUE;
 
        for (; optind < argc; optind++) {
@@ -1082,5 +1112,8 @@ int main(int argc, char *argv[])
        }
 
        twalk(files, visitor);
+
+       deinit_buffers();
+
        return 0;
 }