[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 01/13] util/path: Do not cache all filenames at
From: |
Laurent Vivier |
Subject: |
Re: [Qemu-devel] [PATCH 01/13] util/path: Do not cache all filenames at startup |
Date: |
Thu, 13 Jun 2019 15:40:16 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 |
Le 19/05/2019 à 22:19, Richard Henderson a écrit :
> If one uses -L $PATH to point to a full chroot, the startup time
> is significant. In addition, the existing probing algorithm fails
> to handle symlink loops.
>
> Instead, probe individual paths on demand. Cache both positive
> and negative results within $PATH, so that any one filename is
> probed only once.
>
> Use glib filename functions for clarity.
>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
> util/path.c | 201 ++++++++++++----------------------------------------
> 1 file changed, 47 insertions(+), 154 deletions(-)
>
> diff --git a/util/path.c b/util/path.c
> index 7f9fc272fb..8e174eb436 100644
> --- a/util/path.c
> +++ b/util/path.c
> @@ -8,170 +8,63 @@
> #include <dirent.h>
> #include "qemu/cutils.h"
> #include "qemu/path.h"
> +#include "qemu/thread.h"
>
> -struct pathelem
> -{
> - /* Name of this, eg. lib */
> - char *name;
> - /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
> - char *pathname;
> - struct pathelem *parent;
> - /* Children */
> - unsigned int num_entries;
> - struct pathelem *entries[0];
> -};
> -
> -static struct pathelem *base;
> -
> -/* First N chars of S1 match S2, and S2 is N chars long. */
> -static int strneq(const char *s1, unsigned int n, const char *s2)
> -{
> - unsigned int i;
> -
> - for (i = 0; i < n; i++)
> - if (s1[i] != s2[i])
> - return 0;
> - return s2[i] == 0;
> -}
> -
> -static struct pathelem *add_entry(struct pathelem *root, const char *name,
> - unsigned type);
> -
> -static struct pathelem *new_entry(const char *root,
> - struct pathelem *parent,
> - const char *name)
> -{
> - struct pathelem *new = g_malloc(sizeof(*new));
> - new->name = g_strdup(name);
> - new->pathname = g_strdup_printf("%s/%s", root, name);
> - new->num_entries = 0;
> - return new;
> -}
> -
> -#define streq(a,b) (strcmp((a), (b)) == 0)
> -
> -/* Not all systems provide this feature */
> -#if defined(DT_DIR) && defined(DT_UNKNOWN) && defined(DT_LNK)
> -# define dirent_type(dirent) ((dirent)->d_type)
> -# define is_dir_maybe(type) \
> - ((type) == DT_DIR || (type) == DT_UNKNOWN || (type) == DT_LNK)
> -#else
> -# define dirent_type(dirent) (1)
> -# define is_dir_maybe(type) (type)
> -#endif
> -
> -static struct pathelem *add_dir_maybe(struct pathelem *path)
> -{
> - DIR *dir;
> -
> - if ((dir = opendir(path->pathname)) != NULL) {
> - struct dirent *dirent;
> -
> - while ((dirent = readdir(dir)) != NULL) {
> - if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
> - path = add_entry(path, dirent->d_name, dirent_type(dirent));
> - }
> - }
> - closedir(dir);
> - }
> - return path;
> -}
> -
> -static struct pathelem *add_entry(struct pathelem *root, const char *name,
> - unsigned type)
> -{
> - struct pathelem **e;
> -
> - root->num_entries++;
> -
> - root = g_realloc(root, sizeof(*root)
> - + sizeof(root->entries[0])*root->num_entries);
> - e = &root->entries[root->num_entries-1];
> -
> - *e = new_entry(root->pathname, root, name);
> - if (is_dir_maybe(type)) {
> - *e = add_dir_maybe(*e);
> - }
> -
> - return root;
> -}
> -
> -/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
> -static void set_parents(struct pathelem *child, struct pathelem *parent)
> -{
> - unsigned int i;
> -
> - child->parent = parent;
> - for (i = 0; i < child->num_entries; i++)
> - set_parents(child->entries[i], child);
> -}
> -
> -/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
> -static const char *
> -follow_path(const struct pathelem *cursor, const char *name)
> -{
> - unsigned int i, namelen;
> -
> - name += strspn(name, "/");
> - namelen = strcspn(name, "/");
> -
> - if (namelen == 0)
> - return cursor->pathname;
> -
> - if (strneq(name, namelen, ".."))
> - return follow_path(cursor->parent, name + namelen);
> -
> - if (strneq(name, namelen, "."))
> - return follow_path(cursor, name + namelen);
> -
> - for (i = 0; i < cursor->num_entries; i++)
> - if (strneq(name, namelen, cursor->entries[i]->name))
> - return follow_path(cursor->entries[i], name + namelen);
> -
> - /* Not found */
> - return NULL;
> -}
> +static const char *base;
> +static GHashTable *hash;
> +static QemuMutex lock;
>
> void init_paths(const char *prefix)
> {
> - char pref_buf[PATH_MAX];
> -
> - if (prefix[0] == '\0' ||
> - !strcmp(prefix, "/"))
> + if (prefix[0] == '\0' || !strcmp(prefix, "/")) {
> return;
> -
> - if (prefix[0] != '/') {
> - char *cwd = getcwd(NULL, 0);
> - size_t pref_buf_len = sizeof(pref_buf);
> -
> - if (!cwd)
> - abort();
> - pstrcpy(pref_buf, sizeof(pref_buf), cwd);
> - pstrcat(pref_buf, pref_buf_len, "/");
> - pstrcat(pref_buf, pref_buf_len, prefix);
> - free(cwd);
> - } else
> - pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
> -
> - base = new_entry("", NULL, pref_buf);
> - base = add_dir_maybe(base);
> - if (base->num_entries == 0) {
> - g_free(base->pathname);
> - g_free(base->name);
> - g_free(base);
> - base = NULL;
> - } else {
> - set_parents(base, base);
> }
> +
> + if (prefix[0] == '/') {
> + base = g_strdup(prefix);
> + } else {
> + char *cwd = g_get_current_dir();
> + base = g_build_filename(cwd, prefix, NULL);
> + g_free(cwd);
> + }
> +
> + hash = g_hash_table_new(g_str_hash, g_str_equal);
> + qemu_mutex_init(&lock);
> }
>
> /* Look for path in emulation dir, otherwise return name. */
> const char *path(const char *name)
> {
> - /* Only do absolute paths: quick and dirty, but should mostly be OK.
> - Could do relative by tracking cwd. */
> - if (!base || !name || name[0] != '/')
> - return name;
> + gpointer key, value;
> + const char *ret;
>
> - return follow_path(base, name) ?: name;
> + /* Only do absolute paths: quick and dirty, but should mostly be OK. */
> + if (!base || !name || name[0] != '/') {
> + return name;
> + }
> +
> + qemu_mutex_lock(&lock);
> +
> + /* Have we looked up this file before? */
> + if (g_hash_table_lookup_extended(hash, name, &key, &value)) {
> + ret = value ? value : name;
> + } else {
> + char *save = g_strdup(name);
> + char *full = g_build_filename(base, name, NULL);
> +
> + /* Look for the path; record the result, pass or fail. */
> + if (access(full, F_OK) == 0) {
> + /* Exists. */
> + g_hash_table_insert(hash, save, full);
> + ret = full;
> + } else {
> + /* Does not exist. */
> + g_free(full);
> + g_hash_table_insert(hash, save, NULL);
> + ret = name;
> + }
> + }
> +
> + qemu_mutex_unlock(&lock);
> + return ret;
> }
>
Reviewed-by: Laurent Vivier <address@hidden>
Tested-by: Laurent Vivier <address@hidden>
Thanks,
Laurent
[Prev in Thread] |
Current Thread |
[Next in Thread] |
- Re: [Qemu-devel] [PATCH 01/13] util/path: Do not cache all filenames at startup,
Laurent Vivier <=